« PreviousContinue »
did the copper in the furnace, even at the end where the gas means of the ratio of densities of oxygen and hydrogen formerly entered, show any sign of losing its metallic appearance. given by me, viz. 15.882. Hence Three results, obtained in August, 1892, were :
The following table shows the results arrived at by various , 10.......................... 2 31020
experimenters. Von Jolly did not examine hydrogen.
numbers are multiplied by 1000 so as to exhibit the weights in Mean ... ... ... ... ... 2'31028
grams per litre :--
Air. Oxygen. Nitrogen. Hydrogen. To these may be added the results of two special experiments Regnault, 1847 ...... I'29319 ... 1'42980 ... 1'25617 ... Oʻ089;8 made to test the removal of hydrogen by the cupper oxide. For
Corrected by Crafts .. I'29349 ... 1'43011 ... 1'25047 ... O'08988 this purpose a small hydrogen generator, which could be set in
Von Jolly, 1880 ...... 1-29351 ... 1'42939 ... 1°: action by closing an external contact, was included between the
Ditto corrected........ 1'29383 ... 1'42971 ... 125819 two tubes of reduced copper, the gas being caused to bubble
Leduc, 1891...........1'29330 ... 1'42910 ... 1'25709 ... O 08985 through the electrolytic liquid. The quantity of hydrogen
Rayleigh, 1893 ....... 1'29327 ... 142952 ... I'25718 ... Oʻogoo! liberated was calculated froin the deflection of a galvanometer The correction of Regnault by Crafts (Comptes Rendus, vol. included in the circ it, and was sufficient, if retained, to alter cvi., p. 1664) represents allowance for the contraction of Reg. the density very materially. Care was taken that the small | nault's globe when exhausted, but the data were not obtained stream of hydrogen should be uniform during the whole time from the identical globe used by Regnault. In the fourth row I (about 24 hours) occupied by the filling, but, as will be seen, have introduced a similar correction to the results of von Jolly. The impurity was effectually removed by the copper oxide. 1 This is merely an estimate founded upon the probability that the Two experiments gave
proportional contraction would be about the same as in my own
case and in that of M. Leduc. September 17 ... ... 2431012
In taking a mean we may omit the uncorrected numbers, 20 ... ... 2*31027
and also that obtained by Regnault for nitrogen, as there is
reason to suppose that his gas was contaminated with hydrogen. Mean ... ... 2*31020
Mean Numbers. We may take as the number for nitrogen
Oxygen. Nitrogen. Hydrogen. 2-31026
129347 142961 1'25749 o'o8y91 Correction for contraction ... 56
The evaluation of the densities as compared with water is ex. posed to many sources of error which do not affect the comparison of one gas with another. It may, therelore, be instructive
to exhibit the results of various workers relerred to air as Although the subject is not yet ripe for discussion, I cannot
unity. omi: to notice here that nitrogen prepared from ammonia, and
Oxygen. Nitrogen. Hydrogen. expected to be pure, turned out to be decidedly lighter than the Regnault (corrected) 1'10362 ... 097 138 ... O'06949 above. When the oxygen of air is burned by excess of am v. Jolly (corrected) (10502 ... 0.97245 ... monia, the deficiency is about 1/1000th part.” When oxygen is Leduc......... ...... [1050 ... 0'972 ... 0°05947 substituted for air, so that all (instead of about one-seventh Rayleigh ... ... ... ... 110535 ..097209 ... 0°06960 part) of the nitrogen is derived from ammonia, the deñciency of weight may amount to per cent. It seems certain that the
Mean............ 110525 ... 0.97218 ... o'o6952 abnormal lightness cannot be explained by contamination with hydrogen, or with ammonia, or with water, and everything
As usually happens in such cases, the concordance of the suggests that the explanation is to be sought in a dissociated
numbers obtained by various experimenters is not so good as state of the nitrogen itself. Until the questions arising out of
might be expected from the work of each taken separately. The these observations are thoroughly cleared up, the above number
most serious discrepancy is in the difficult case of hydrogen, for nitrogen must be received with a certain reserve. But it
M. Leduc suggests (Comptes Rendus, July, 1892) that my nam
ber is too high on account of penetration of air through the blowhas not been thought necessary, on this account, to delay the
off tube (used to establish equilibrium of pressure with the presentation of the present paper, more especially as the method
atmosphere), which he reckons at l m. long and I cm, in employed in preparing the nitrogen for which the results are
diameter. In reality the length was about double, and the recorded is that used by previous experimenters.
diameter one-half of these estimates; and the explanation is Reduction to Standard Pressure.
difficult to maintain, in view of the fact, recorded in my paper,
that a prolongation of the time of contact from 4m to zo had The pressure to wbich the numbers so far given relate is that no appreciable ill effect. It must be admitted, however, that due to 762-511 mm, of mercury at a temperature of 1485, there is a certain presumption in favour of a lower number, and under the gravity operative in my laboratory in latitude unless it can be explained as due to an insufficient estimate for 51° 47'. In order to compare the results with those of other the correction for contraction. On account of the doubt experimenters, it will be convenient to reduce them not only to
as to the appropriate value of this correction, no great 760 mm. of mercury pressure at oo, but also to the value of weight can be assigned to Regnault's number for hydrogen. 10 gravity at Paris.
the atomic weight of oxygen be indeed 15.88, and the ratio of The product of the three factors, corrective for length, for
densities of oxygen and hydrogen be 15.90, as M. Ledus makes temperature, and for gravity, is o‘99914. Thus multiplied, the them, we should have to accept a much higher nuinber for the numbers are as follows:
ratio of volumes than that (2'0002) resulting from the very
elaborate measurements of Morley.
But while I write the in-
formation reaches me that Mr. A. Scott's recent work upon the
volume ratio leads him to just such a higher ratio, viz. 2'00245. and these may now be compared with the water contents of the a number a priori more probable than 2.0002. Under the cir. globe, viz. 1836-52.
cumstances both the volume ratio and the density of hydrogen The densities of the various gases under standard conditions, must be regarded as still uncertain to the 1/1000th part." referred to that of distilled water at 4°, are thus:Air. Oxygen.
Nitrogen. 0:00! 29327 0:00142952
ELECTRICAL RAILWAYS.1 0.00125718
TONE of the most striking of the many new departures in the With regard to hydrogen, we may calculate its density by O
practical application of electrical science, which made the 1 Much larger quantities of hydrogen, sufficient to reduce the oxide over Paris Exhibition of 1881 memorable, was a short tramway laid several centimetres, have been introduced without appreciably altering the weight of the gas.
1 Bulletin des Séances de la Société de l'hysique. ? NATURE, vol. xlvi. p. 512.
9 Friday evening discourse delivered at the Royal. Institution by Dr. The thermometer employed with the manometer read o 15 too high. Edward Hopkinson on February 24.
down, under the direction of the late Sir William Siemens, 1 additional sum equivalent to the charge for its actual consumpfrom the Palais de l'Industrie to the Place de la Concorde, tion for 1440 hours. upon which a tramcar worked by an electric motor plied up and In one respect water power has an economic advantage over down with great regularity and success during the period of the steam power, because alihough steam engine and turbine alike Exhibition. Yet few of those who saw in this experiment the work with greatly reduced efficiency at reduced loads, when possibilities of a great future for a new mode of traction would the turbine gates are partially closed and the water restrained in have ventured to predict that within ten years' time, in the the reservoir, it is not subject to loss of potential energy, United States alone, over 5,000 electric cars would be in opera whereas the energy of the steam held back by the valves of the tion, travelling 50,000,000 miles annually, and carrying engine suffers loss through radiation and condensation. 250,000,000 passengers, or that electrical traction would have At Bessbrook the turbine and generator dynamo combined solved the probiem of better communication in London and yield 60 per cent. of the energy of the water as electrical energy other large cities. Two years before the exhibition in Paris the available for work on the line, but when the load is reduced to iate Dr. Werner Siemens had exhibited at the Berlin Exhibition a third of the full load the efficiency is reduced to 33 per cent.
experimental electric tramway on a much smaller So on the City and South London line a generator engine and scale, and his firm had put down in 1881 the first permanent dynamo will yield, when working at their full load, 78 per cent. electric railway in the short length of line at Lichterfelde, near of the indicated horse-power as usesul electrical power, but at Berlin, which, I believe, is still at work. In the same year Dr. half load the efficiency falls to 65 per cent. Notwithstanding William Siemens undertook 10 work the tramway, then pro These conditions the generator station of the City and South jected, between Portrush and Bushmills, in the north of Ireland, London line is producing electrical energy at a cost of 1.56d. per over six miles in length, by electric power, making use of the Board of Trade unit, which is less than the annual average cost water power of the Bush River for the purpose, an underlaking of production of any electric station in England, with the single which I had the advantage of carrying out under his direction. exception of Bradford, which has the advantage hoth of cheap It is no part of my object to.night to follow further the history coal and cheap labour. In output it is the largest of any Electric of electric traction, which is so recent that it is familiar 10 Generating Station in England, the total electrical energy all; but, in alluding to these initial stages of its development, delivered in 1892 being 1,250,000 Board of Trade units, the I have desired to recall that it was to the foresight and energy of second on the list being the St. James and Pall Mall wi'h Dr. Werner and Dr. William Siemens, and their skill in apply. 1,186,826 units. ing scientific knowledge to the uses of daily life, which gave Let us pass now to the consideration of the distribution of the the first impulse to the development of the new electrical power. electric power along the line. I have equipped the three model
The problem of electric traction may be naturally considered tracks before you with three different kinds of conductors. In under three heads :
two of them the rails of the permanent way, which are (1) The production of the electrical power.
necessarily uninsulated, are made use of for the return current. (2) Its distribution along the line.
This plan, with I believe the almost single exception of the (3) The reconversion of electrical into mechanical power, in Buda Pesih Tramway, has been universally adopted with the the car motor or locomotive.
object of saving the cost of a return conductor ; but it is doubtThe first of these here in England at any rate is dependent ful whether such an arrangement can be considered final, for it upon the economical production of steam power, although there must necessarily create differences of potential in the earth, which are essential points of difference between the conditions under already in some instances have had disturbing effects upon our which steam power is required for electric traction purposes and observatories, or upon our telegraph and telephone systems. It for electric lighting. But in Scotland and Ireland and in many appears to be probable in the more or less distant future that the countries abroad there is abundant water power, now only very use of the earth for the passage of large current will be guarded partially utilised. The Portrush line is worked in part by water by legislation ; and ihat it will be reserved for the more delicate and in part by steam power, but in the Bessbrook and Newry and widely extended operations of telegraphy and telephony. Tramway (of which ihere is a working mollel on the table) These disturbances may of course be easily avoided by the use water power is exclusively iised.
of an insulated conductor for the return circuit. In the case of A few experiments will show that the demand for power on conductors which are in such a position that contact may be the generating plant is greatest at the moment of starting made from them to the ground through the body of a horse or the car or traill, when in addition to the power required to over some other animal coming into contact with them, there is come the frictional resistances power is also required to accelerate another strong argument for an insulated return, as many the velocity. Thus, if instead of a single car ihere are a number animals, and notably horses, are far more sensitive to electric of trains moving on the one system, and it so happens that shock than man. It is not perhaps well known, but still a fact, several are starting together, the demand made upon the gener | thai a shock of 250 volts is quite sufficient to kill a horse almost ating plant may at one moment be three or four times as great instantaneously. as that made a few seconds aller. This is shown in the diagrams The first model has a single overhead conductor with return which exhibit the variation of current supplied by the generators by the rails; but in place of a single fishing rod collector or on the City and South London Railway, with eight trains run trolley to take the current from the overhead wire there are fixed ning together, the readings being taken every ten seconds. The on the car two rigid bars, one at each end, which slide along maxima rise as high as double the mean ; thus the generating the under surface of the wire and make a rubbing contact against plant must be capable of instantly responding to a demand it. This system, devised by Dr. John Hopkinson, has the double or even treble the average demand upon it.
advantage ihat there is less difficulty in maintaining contact on In electric lighting it is true there is not less variation between uneven roads or on curves, and that the catenaries of the sus. the maximum demand and ihe mean taken during the ordinary | pended wire may be hung with greater dip, and therefore with hours of lighting, but it is only in the event of sudden fog that less tension. Again, the double contact obviates the frequent the probable demand cannot be accurately gauged beforehand, breaks and consequent sparking of a single trolley system. The and provided for by throwing more generators into action. Thus second morlel shows the system adopted on the City and South in a lighting station each generator may be kept working London line, and more recently followed on the Liverpool Overapproximately at its full load, and therefore under conditions of head line, ot a conductor of channel steel, upon which collectors maximum economy, whereas in a traction station the whole fixed to the locomotives make a sliding contact. The third plant must be kept ready to instantaneously respond to the track shows an overhead system like the first, but with an insumaximum deinands which may be made upon it, and must there. lated return in place of return by the rails. fore necessarily work with a low load factor, and consequently The characteristic feature of an electric motor is that it clewith diminished economy. So important is the influence on livers us the mechanical power we require directly in the form cost of production of the possible demand in relation to average of a couple about an axis instead of in the form of a rectilinear demand, that the Corporation of Manchester under heir force, as is the case with steam, gas, or air engines, which order for electric supply, have lecided upon the advice of must be reduced to a rotary form by connecting rod and crank. their engineer to annually charge a customer k3 per quarter Thus it is possible to sweep away all intermediate gear, and to for each unit per hour of maxiinum supply which he may arrive at once at the simplest of all forms of a traction motor, require, in addition to 211, per unit for each unit actually consisting of but one pair of wheels fixed on a single axle with cousumed, i.e. for being ready to supply him with a certain the armature constructed directly upon it, with its magnets susamount of electrical power if required to do so, they charge an pended from it and maintained in their position against the
magnetic forces acting upon them by their weight. Such a of the magnet coils. If it were possible to use alternate current locomotive is shown in the third model before you. So far as I motors for traction work the difficulty could at once be met by am aware, a locomotive of such simplicity as this has never been introducing a transformer in the circuit, and placing the motor constructed for practical work, but on the City and South in its secondary. The effective convolutions of the secondary London line the armatures of the motors are placed directly on circuit on the transformer could then be varied as the speed the axles and the magnets, suspended partly from the axles and increases in such wise that the electro-motive force of the line partly from the frame.
is balanced by the back electro-motive force of the motor and The second model is an exact reproduction of the locomotives the fall of potential due to the resistance of the motor coils, on the City and South London line, but with a different arrange so avoiding all need for resistances. ment of motors. Here both armatures are included in the same The City and South London line has enabled experiments to be magnetic circuit, and both magnets and armatures carried on the made on the efficiency of the railway system as a whole, taking into frame of the locomotive and not on the axles. The armatures are account the loss of power in the generators, on the line, and geared to the axles by diagonal connecting rods, the axle boxes in the motors, and in the resistances of the locomotives. The being inclined, so that their rise and fall in the horn hlocks is at loss in the line is about eleven per cent of the power generated, right angles to the connecting rods. This design, which is due and the efficiency of the locomotives as a whole is, as I have to the late Mr. Lange, of Messrs. Beyer, Peacock & Co., shown, 70 per cent. ; thus the electrical efficiency of the entire allows of the motor armature being placed on the floor level of system is 62 per cent. The trains weigh with full load of 100 the locomotive, and so more easily accessible,
passengers about forty tons, and the average speed between This model will serve to show some of the characteristic stations is 13.5 miles per hour. The cost of working, including features as well as some of the characteristic defects of an all charges, during last half year was 7'1d. per train mile, of electric motor as such. But in order to show these clearly I which 4 7d. represents the cost of production of the electric may refer for a moment to the general theory of a motor. It is power, and 2.411. the cost of utilising it on the locomotives. It easily shown that in a series wound motor the couple or turning is perhaps hardly a fair comparison to compare the cost of workmoment on the axle is a function of the current only, and ing such a line as the South London line with the cost of steam independent of the speed and electro-motive force. Again it traction on other lines, inasmuch as steam could not possibly be follows from Ohm's law that the current passing through the | used in the tunnels, only 10'6" diameter, in which this line is motor multiplied by the resistance of the magnet and armature constructed, but the comparison is not uninstructive. Take the coils is equal to the difference between the electro-motive force Mersey Railway, where the gradients and nature of the traffic at the terminals of the motor and the electro-motive force are similar. On the Mersey Railway the locomotives weiga which would be generated by the motor, if it were working at about 70 tons, and the train, which is capable of carrying about the same speed as a generator of electricity, that is to say the 350 passengers, 150 tons. According to the published returns difference between the electro-motive force at the terminals of the company the cost of locomotive power is 14d. per train and what is called the “back" or "counter" electro-motive mile, i.e. double the cost on the South' London line, but for a force of the motor. Hence if the terminals of the motor be | train weighing between four and five times as much but capable coupled direct to the line at the moment of starting when the | of carrying only 3 times the number of passengers ; thus the motor is still at rest, the current will be very great and its power cost of steam traction per ton mile of train is about half that per entirely absorbed in the coils of the armature and magnets, ton mile of train for electric traction. But it is not on the cost but the turning moment will then be a maximum. The motor per ton mile that the success of a passenger line depends. The then begins to move, part of the power being spent in overcom real basis of comparison is the cost per passenger mile, and here ing frictional resistances and part in accelerating the train. A electric traction has great advantage over steam, as the dead back electro-motive force is then set up, increasing as the weight of the electric motor is small compared with the dead speed increases, and causing the current to diminish until finally weight of steam locomotives of the same power, and with electric a position of equilibrium is established, when the speed motors the trains can be split up into smaller units at but slightly is such that the back electro-motive force together with the increased cost, so permitting a more frequent service. We canloss of potential in the coils of the motor is equal to the not expect, therefore, that electric traction with our present potential of the line. But in practice the mechanical strength of knowledge will take tbe place of steam traction on our trunk The motor, and the carrying power of its coils, as well as the lines ; but it has its proper function in the working of the underlimited current available from the generators makes it necessary ground lines now projected for London, Paris, Berlin, and to introduce resistances in circuit with the motor to throttle the Brussels, and other large towns, and also I think on other urban current and to reduce it within proper limits. It is to this point lines, sor example, on the Liverpool Overhead Rail way, where I desire to draw attention, that in traction work when starting trains of large carrying capacity are not required, but a frequent the motor resistances must be introduced, which, with the service is essential; and finally, also on those short lines, whether resistance of the motor itsell, at the moment of starting, absorb independent or branches of the great trunk lines where water the whole power of the current, reducing the efficiency of the motor power is available. When I undertook the construction of the to nil, and which continue to absorb a large percentage of the Bessbrook line it was a condition that the cost of working should power, until the condition of equilibrium is established. This is be less than the cost of working by steam, a condition which the great defect in electric motors for traction work, and its im. the fust six months of working showed to be successfully falportance can be shown very clearly by reference to the work | filled. When Messrs. Mather and Platt undertook the condone on the City and South London line. There the motors struction of the electric plant for the City and South London when working with their normal current have an efficiency of Railway, they guaranteed that the cost of traction for a service 90 per cent., but the actual all-round efficiency of the locomo of 8247 miles per week as actually run should not exceed 637 tives as a whole is 70 per cent, only, so that the loss in starting per train mile, exclusive of the drivers' wages. Their anticipa. is equal to 20 per cent. of the whole power. Of course in some tions have been more than realised, the actual cost being respects the City and South London line is exceptional in that a 5'1d. per train mile only. There are, however, other projects start is made every two or three minutes. Various devices have both in America and on the continent for electric railways on been sugge-ted with a view to diminishing this waste of power in which the special feature is to be an enormously bigb speed of starting an electric motor, but none entirely meet the case. travel, speeds of 150 and even 200 miles per hour being promised. Thus if the locomotive or car has two motors, these can be With a steam locomotive, involving the reciprocating motion of coupled in series at the start, and subsequently thrown into the piston and connecting rod, such speeds are probably unparallel, thereby doubling the tractive force with a given current, attainable, but they may be realised in the purely rotary motion or for the same tractive force reducing the loss of power by of an electric motor. But at such high speeds as these the three-fourths. When through the increase of speed of the motor power required to overcome the air resistance is of special conthe back electro-motive force balances the electro-motive force | sideration. Probably up to speeds of 750 miles per hour, or of the line the speed can be increased by diminishing the even to higher limits still, the ordinary law of air resistance bolds magnetic field by reducing the effective coils on the good, as the rate of disturbance is still less than the velocity of magnets, but this device does not give any assistance at the waves in air, but above these limits we leave the regions of lower speeds, as the magnets ought to be so wound as to be ordinary locomotion and enter rather into the field of projectiles. high on the characteristic curve, or nearly saturated, with the Assuming, however, that the ordinary laws of air resistance do normal current, and it is therefore not possible to obtain hold good, I calculate that the power required to propel do any increased intensity of field, by increasing the convolutions ordinary train 200 feet long at 200 miles per hour against the
resistance of air alone, apart from the frictional resistances, October 10, a similar storm passed over from Wilcannia to would not be less than 1700 horse power. Though there is Sydney, a distance of four hundred and eighty miles, at the nothing to prevent the construction of electric locomotives cap. rate of fifty-five miles per hour ; and I have before traced one able of developing this or even greater power, the strength of over the same part of the colony, the rate being fifty-seven miles the materials at present at command will set a limit to the speeds per hour, but we have not traced a sufficient number to deterwhich may be obtained.
mine an average rate. In order that the engineer 'may realise the imperfection of all As to the velocity of the wind along the line of damage in his works, it is well for him to be constrained from time to time these storms, we have no actual anemometer results, so far we to contemplate the amount of energy involved in his final pur- have not had one which passed over one of the anemometers, pose compared with the energy of the coal with which he starts. but judging from the damage done to large and solid trees, I have endeavoured to put before you to-night the losses that two and even three feet in diameter, it cannot I think be occur and the reasons for them, in some steps of the complex less than one hundred and forty or one hundred and fisty miles machine which constitutes an electric railway, so in conclusion per hour. I will draw your attention to the ultimate efficiency of the We may now turn to the storms in the Narrabri district. The machine, starting with the coal and ending with the passenger storm reached Narrabri at 6.15 p.m., and the postmaster reports carried through space. The diagram on the wall, starting with that the storm which approached Narrabri from north-west was the familiar 12,000,000 foot-pounds, the energy of a pound of accompained by thunder and lightning, but no hail. The wind. coal, shows the loss in each step, supposing it made with the however, seems to have been of hurricane violence, trees two feet most economical appliances known to the engineer, first in in diameter were torn up by the roots, limbs twelve inches through the boiler, then in the steam engine, generator dynamo, con were snapped off short, a brick factory completely ruined, ductors, locomotives, in the dead weight of the train, till finally roofs, sign-boards, and everything that the wind could move we arrive at the energy expended on the passenger himself, went Aying ; in the language of the local newspaper, "sub. which we find to be 133,ooo foot-pounds, or but little more than
stantial' brick buildings came tumbling in all directions, the I per cent. of the energy with which we started. It is true indeed that transportation is a more economical process than lighting with incandescent lamps, in which the final efficiency is about one-half per cent., but whether in lighting or in traction, when we consider that ninety-nine parts are now wasted for one part saved, we may realise that the future has greater possibilities than anything accomplished in the past.
- - - - - HAIL STORMS." SOME recent thunder and hail storms were so violent that they
call for more than a passing notice, not only on account of their severity, but also because they are well marked phenomena in our weather. The district in which they were most severe is that around Narrabri, and the weather map for the day indicated this district as one in which storms would probably manisest great intensity. The places from which the best accounts have reached me are Narrabri, Avondale, thirty miles due north of Narrabri, and Tulcumbah, fifty-seven miles south-east of Narrabri.
The Sydney weather chart at 9 a.m. on October 13, the day of these storms, shows us that there was but little difference in pressure all over Australia. To the west of the overland telegraph line it was slightly higher, over western New South Wales and Queensland lower, and higher again over the East Coast, in which the isobars clearly outline the area of relatively low pressure, and the kinks in them indicate disturbed conditions, local short-lived storms, and before tbe day was over the inserence from the state of pressure was fully justified, for storms of extreme violence occurred over the area; storms which swept down great forest trees two and three feet in diameter. What this
Photograph of iron perforated by hail. means in wind velocity I am unable to say, the trees are eucalypts, air was full of iron tubs, galvanised iron, and tins of every and therefore the wood is hard and very strong, but they were description." treated as if they were reeds, and their strength was as nothing In ihe district south of Narrabri the storm was even more compared with the force of the wind.
severe. At Tulcumbah Station, fifty-seven miles south-east from These storms are common enough, but owing to the sparse Narrabri, at 8 p.m. on October 13, a violent thunder and hail population they seldom pass over towns or dwellings. In this
storm broke over the homestead. It lasted half an hour, and instance such has been the case, and in the future as population Mr. A. D. Griffiths, my informant and manager of the station, increases similar cases must increase in number, for the storms says, “I measured some of the hailstones, six and a half inches are abundant, indeed these storms form a well-marked feature of
in circumference; this was fifteen or twenty minutes after the our summer weather. As a rule they are disconnected, and the
storm, and I think I did not get the largest. Next morning I most violent part of the wind covers but two hundred or three
| found that nineteen sheep had been killed by the hail, also birds, hundred yards wide, and travels along with great rapidity, leav. kangaroo-rats, and other animals were found lying dead in all ing a narrow line of destruction in its wake.
directions. All the windows exposed to the storm were broken, On the day in question heavy storms were reported at Good.
and the galvanised iron roofing is dented from end to end, and ooga, Armidale, two hundred and forty miles south-east of many sheets cut through : in several cases the hailstones went Goodooga, and at Graston one hundred miles norih-east of Armi. through the iron; in one sheet I found thirty holes, and in another dale. Storms which seem to have been quite disconnected, for more than sixty. The bark of the trees in the storm track was all the earliest time was at Graston, and as a rule they come from battered by the hail, and the fences and buildings bore traces of the west ; these are spoken of as severe storms, but were evidently the impact of these great lumps of ice. The stones were genernot specially remarkable, nothing to compare with those in the ally triangular or conoidal in form, many having an uneven sur
arrabri district to which I wish to direct your attention. Un- face, which looked as if it had been formed from frozen drops of fortunately, data for determining the rate of progress is not avail. water collected into masses; others had an opaque snow-like able, although that as to the intensity of the storms is abundant. centre, perhaps the majority were like ihis, the remainder being I may mention that three days before these storms, that is on like clear ice. It was only the larger stones that were irregular Read by H. C. Russell, F.R.S. before the Royal Society of N. S. Wales,
as described, the smaller ones were generally rounded."
At Avondale, thirty miles north of Narrabri, my informant,
November 2, 1892.
Mr. S. J. Dickson, says, “From the gth to the 13th of October, were exhibited, the originals of which had been taken by Prof. the weather was unusually oppressive with threatening storms, | Mach.- A paper on the differential equation of electric flow was and on the evening of the 13th a heavy storm was seen to be work read by Mr. T. H. Blakesley. The object of the paper is to ing up from the west accompanied by incessant lightning of every show that the ordinary mathematical expressions for electric description, and about 8 p.m. it broke over the homestead in all Aow fail to explain all known facts, and to point out that in its fury, the wind was from south-west and of terrific force, and order to interpret these facts certain properties of matter not the rain and hail were very severe. The hailstones were as large usually recognised must be admitted. The subject is treated as hen-eggs, and in some of the paddocks, one particularly, it both algebraically and geometrically, in the latter case the pounded the herbage completely out, so that not a vestige of it magnitudes being represented by the projections of the sides of was left, although before the storm came on it was from six to a triangle revolving in its own plane on a fixed line in that plane. twelve inches high, and in other places strong variegated thistles Taking the ordinary differential equation for a simple circuit three to four feet high were beaten down. Trees some two feet thick, that the wind could not tear up by the roots, were snapped having resistance and self-induction, viz., V- Ldt = RC, it is off short as if made of matchwood. In the storm the hail killed shown that this takes no account of any energy except that birds innumerable, and even domestic fowls roosting on the trees spent in heating the conductor, and that where radiation into were killed by it, and after the storm a large snake was found space is concerned, it is necessary to introduce another term AC, cut into two pieces by the hail, so at least it appeared. On the where 1 is a quantity of the nature of resistance. It is further open plain the hail laid four to six inches deep, and the whole pointed out that if work be done outside the circuit, the line country looked as if a heavy snowstorm had passed over it. Trees which geometrically represents the induced E.M.F. cannot be in the track of the hail were completely denuded of leaves, and the perpendicular to that indicating the current and "effective" bark knocked off tree trunks and limbs. The storm wind carried E.N.F., the latter term being defined to mean the value of the away outstations, unroofed the hayshed, damaged the woolshed, quantity which is numerically equal to the product of the current and carried away two sides of the house.verandah, and the sheets into the resistance. A magnetic phase-lag must therefore exist. of iron from it were found nearly half a mile (zo chains) away to The author also shows that a magnetic field induced in phase the north-east, round wall plates in the hayshed six to eight inches with the magnetic induction would not result in a loss of energy, thick were broken to pieces, and the iron roofing on all the build. and no hysteresis could exist. Under the same circumstances ings was battered by the hail as if some one had pounded it with
there could be no radiation of energy from an alternating a hammer all over. The storm track was only a mile to a mile
magnet. A Leyden jar discharging through a circuit having and a half wide, at least the hail part. Between 7 and 8 p.m., sell-induction is next considered. Taking the ordinary premises as the storm came up, there seemed to be a white bow in the it is shown that no provision is there made for energy radiated sky, like a white rainbow stretching from north to south. I
into space, and that magnetic lag is nece-sary for the existence have seen heavy storms before, but I never wish to see another
of such phenomena. The differential equations for the variables like this. The shearers were completely terrified, and all say in condenser discharges according to ordinary assumptions are that they have never experienced a storm like it, in fact, it
shown to be of the same form, and the variables can be reprebeggars description and can hardly be realised. It was an
sented by the projection of the sides of a triangle which is experience that we shall remember as long as we live.”
simultaneously undergoing uniform rotation and linear logarNorth of Narrabri, and especially between Narrabri and ithmic shrinking. The rate of shrinking is the same as that of Avondale, the storms were very severe. Midway between these
the radius vector of an equiangular spiral of characteristic angle 8, places and at Terry-hi-hi and Berrigal Creek the wind worked
KR great destruction in the forest. How violent it was may be where cosB = V i : 2; K, L, and R representing capacity, gathered from the fact that great trees twelve feet in circum:
self-induction, and resistance respectively. The equations and ference at three feet from the ground, were snapped off short ten feet above the ground, or entirely stripped of their limbs.
their consequences are considered at sonie length, and several important properties brought out. To allow for radiated energy,
R must be virtually increased from R to R +4, and the total SCIENTIFIC SERIAL.
energy is divided between the circuit and the field in the ratio of American Meteorological fournal, March.-Exploration of
R to X. If, therefore, the circumstances be such that A is large the free air, by Prof. M. W. Harrington. The author considers
compared with R, say by having high frequency, the heating of
the circuit may only be a small part of the total energy. In that the conclusions to be drawn from weather maps are nearly
s are nearly this direction the author thinks the true explanation of some of exhausted, and that the reason of the imperfection of meteoro | logy is the want of knowledge of what is going on in the free
Tesla's experiments is to be found, the energy being expended
chiefly in radiation and not in current through the experimenter's air. Mountain observations give most important results, but
body. Prof. Perry thought the CPR term would not represent they are still sursace observations. We know what goes on at
the heating of the wire when the oscillations were rapid, owing the base of a cyclone, but not what occurs at the top. Theories are deduced from cloud observations, but we lack actual know
to the distribution of current not being uniform over the
section of the conductor. Maxwell had shown that certain ledge of what is going on above, and the only means available i
throttling terms had to be considered. In condenser at present is systematic balloon observations. Prof. Harrington thinks that such observations should be provided for by sunds
discharges the complete equation would have many terms.
Prof. O. J. Lodge said the best definition of R in such case. from private sources.—The general winds of the Atlantic Ocean,
was that derived from Joule's law rather than that of Ohms by Prof. W. M. Davis. The basis of this discussion is the " Sailing Directory of the Atlantic Ocean," published by the
Frequency was very important in the radiation of energy, but
even at ordinary frequencies of alternators some energy was Deutsche Seewarte, and especially two generalised wind charts
radiated. Referring to Tesla's experiments, he said the reason contained in the atlas accompanying that work. The author classi
why no serious consequences followed, was that there was not fies the winds as planetary (due to the earth's rotation and the influence of the sun), terrestrial (the annual migration of the
much energy behind them. High frequency might be instruwind belts north and south, and the seasonal variations of
mental in preventing injury, but this he thought remained to be velocity and direction), including the interruptions of continents
proved. Dr. Sumpner pointed out that losses other than C'R and mountain ranges.
(R being the ordinary resistance of the conductor) had to be The colours of cloudy condensation, by
taken into account. In some cases, such as transformers on Prof. C. Barus. The author considers the problems connected
open circuit, the effective resistance might be 1000 times that with the condensation of water from moist air, and reviews the
of the coil. To discuss completely the problem taken up by labours of Mr. Aitken and Mr. Bidwell with reference to the
Mr. Blakesley, it would be necessary to take account of nonparticles of an opaque steam-jet. He also gives a minute de scription of the apparatus employed in his own investigations.
uniform distribution of current, both across and along the conductor, as well as the characier of the magnetic and electric
fields surrounding the circuit. Mr. Swinburne thought there SOCIETIES AND ACADEMIES.
was a tendency to over-estimate the rate of high-frequency
currents, for unless the coils of transformers were asumed LONDON.
geometrically coincident, calculations were difficult. Errors of Physical Society, March 24.-Prof. A. W. Rücker, F.R.S., 1 hundreds per cent. were quite possible. In Tesla's experimenti President, in the chair.-Several excellent photographs of Aying no great power was involved, for the transformer could on bullets and of the air waves produced by vibrating hammers, give out any large power. Mr. Blakesley, in reply, said the