Locusts in the Red Sea.

A GREAT flight of locusts passed over the s.s. Golconda on November 25, 1889, when she was off the Great Hanish Islands the Red Sea, in lat. 13° 56 N., and long. 42° 30 E. The particulars of the flight may be worthy of record.

It was first seen crossing the sun's disk at about 11 a.m. as a tense white flocculent mass, travelling towards the north-east at rout the rate of twelve miles an hour. It was observed at noon the officer on watch as passing the sun in the same state of nsity and with equal speed, and so continued till after 2 p.m. The light took place at so high an altitude that it was only visible when the locusts were between the eye of the observer and the sun; but the flight must have continued a long time after 2 p.m., as numerous stragglers fell on board the ship as late as

Some of us on board amused ourselves with the calculation that, if the length and breadth of the swarm were forty-eight miles, its thickness half a mile, its density 144 locusts to a cubic foot, and the weight of each locust of an ounce, then it would have covered an area of 2304 square miles; the number of insects would have been 24,420 billions; the weight of the mass 42,580 millions of tons; and our good ship of 6000 tons burden would have had to make 7,000,000 voyages to carry this great host of locusts, even if packed together III times more closely than they were flying.

MJ. Wilson, the chief officer of the Golconda, permits me to say that he quite agrees with me in the statement of the facts given above. He also states that on the following morning another flight was seen going in the same north-easterly direction from 415 am. to 5 a. m. It was apparently a stronger brood and more closely packed, and appeared like a heavy black cloud

un the horizon.

The locusts were of a red colour, were about 24 inches long, and of an ounce in weight. G. T. CARRUTHERS.

A Marine Millipede.

It may interest "D. W. T." (NATURE, December 5, p. 104) to know that Geophilus maritimus is found under stones and sea weeds on the shore at or near Plymouth, and recorded in my "Fauna of Devon," Section "Myriopoda," &c., 1874, published in the Transactions of the Devonshire Association for the Advancement of Literature, Science, and Art, 1874. This species was not known to Mr. Newport when his monograph was written (Linn. Trans., vol. xix., 1845). Dr. Leach has ven a very good figure of this species in the Zoological Many, vol. iii. pl. 140, Figs. 1 and 2, and says: "Habitat in iritannia inter scopulos ad littora maris vulgatissime." But, far as my observations go, I should say it is a rare species. See Zoologist, 1866, p. 7, for further observations on this EDWARD PARFITT.

animal.

Exeter, December 9, 1889.

Proof of the Parallelogram of Forces.

Το

THE objection to Duchayla's proof of the "parallelogram of forces" is, I suppose, admitted by all mathematicians. hase the fundamental principle of the equilibrium of a particle on the "transmissibility of force," and thus to introduce the conception of a rigid body, is certainly the reverse of logical procedure. The substitute for this proof which finds most favour with modern writers is, of course, that depending on the "parallelogram of accelerations." But this is open to almost as serious objections as the other. For it introduces kinetic leas which are really nowhere again used in statics. I should therefore propose the following proof, which depends on very elementary geometrical propositions. The general order of argument resembles that of Laplace.

I adopt the "triangular" instead of the "parallelogrammic ferm. Thus, if PQ, QR represent in length and direction any directed magnitudes whatever, and, if these have a single equi lent, that single equivalent will be represented by PR.

To prove that the equivalent of PQ, QR is PR.

(1) The equivalent of two perpendicular lengths is equal in length to their hypothenuse.

For, draw AD perpendicular to hypothenuse BC.

OP = OQ, QP = ON, NQ, QR, RP = OM, MP.

(4) Finally, by (1), theorem holds for isosceles right-angled triangle; .. by (2) it holds for right-angled triangle containing angle 90° 2"; .. by (3) it holds for right-angled triangle containing angle m. 90° 2": i.e. for any angle (as may be shown, if considered necessary, by the method for incommensurables in Duchayla's proof).

Hence, if AD be perpendicular on BC in any triangle,
BA, AC = BD, DA, AD, AC

BC. Q.E.D. W. E. JOHNSON.

Llandaff House, Cambridge, November 12.

Glories.

MR. JAMES MCCONNEL asks in NATURE (vol. xl. p. 594) for acccounts of the colours and angular dimensions of glories. I saw a good instance of the phenomenon on Lake Superior, June 17, 1888, and, having had my attention called to the value of accurate descriptions in such cases by Mr. Henry Sharpe's "Brocken Spectres," I examined it carefully.

The shadow of my head on the mist was surrounded by a brilliant halo or glory, slaty-white around the head, followed by orange and red; then a circle of blue, green, and red, and the same colours repeated more faintly. The diameter of the innermost and brightest circle of red, as measured on the graduated semicircle of a clinometer, was 4°. There was also a very distinct, but nearly white, fog-bow outside, of 42° radius, as measured in the same way. A. P. COLEMAN,

Faraday Hall, Victoria University, Cobourg, Ontario.

Fossil Rhizocarps.

REFERRING to Sir William Dawson's note on this subject in NATURE of November 7 (p. 10), we regret that we have been unable to trace the original source from which the statement in our "Hand-book of Cryptogamic Botany " was derived, relative to the fructification of Protosalvinia or Sporangites. The sentence will therefore, with apologies to Sir W. Dawson, be removed from future editions of the work.

ALFRED W. BENNETT.

The Arc-Light.

WOULD you or any of your readers kindly tell me where I may find an account of any of the latest methods of determining the back E. M. F. of the arc-light? JOSEPH MCGRATH.

Mount Sidney, Wellington Place, Dublin.

THE HYDERABAD CHLOROFORM

COMMISSION.

THE HE appointment of a Commission at the present time to investigate the action of chloroform as an anææsthetic might to many seem an anomaly. For the use of chloroform as an anæsthetic was introduced over forty years ago: it was in November, 1847, that Prof. Simpson, of Edinburgh, first brought this valuable agent before the medical profession. Since that time, the use of chloroform has enormously extended, especially in our country, and although there are other valuable agents of the same class—such as ether and nitrous-oxide gasyet there is a universality of opinion that the employment of chloroform has in many cases a special advantage. Considering the extensive use of the agent, and the progress which has been made of late years in the study of the action of drugs in man, it certainly is surprising that the knowledge of the effect of chloroform on the different parts and organs of the body is not complete. This is not altogether from want of attention to the subject; because, previous to the Hyderabad Commission, at least two Commissions were appointed with the view of investigating the action of chloroform and its occasional serious effects. These Commissions were appointed by the Royal Medical and Chirurgical Society of London, and by the British Medical Association, and they were composed of men who, from their knowledge of experiment and acquaintance with practical medicine, were competent to discuss the question. The two Commissions arrived at the same conclusions as the distinguished French man of science, Claude Bernard, had published years before, and these conclusions tallied with the teaching of the great

London medical schools.

Chloroform and other anaesthetic agents have a peculiar position they are powerful drugs used, not for disease itself, but for the purpose of allowing an operation to be performed, preventing the pain which would otherwise be felt, and relaxing the contraction and spasms of the muscles, so that the surgeon can more readily and accu

rately operate. The administration of the anæsthen something, then, outside the diseased condition; so 2 its use ought theoretically to be perfectly harmless to sick person. Unfortunately it is not always 30 deaths from chloroform are, although rare, by no me unknown. The administrator of chloroform is there re a person of great responsibility he has to watch care. the effect of the agent on the patient, to notice = unfavourable change that occurs, and to adopt measu to counteract any bad effects which appear. knowledge of the mode in which chloroform cate danger to the life of the patient is therefore of vast portance; for, if the administrator knows the sign danger, there is more likelihood of counteracting a ta result. These fatal results, which are among the sad.: that occur in medical practice, ought, if possible, to avoided.

What, then, is the danger to life of chloroform? Or speak more fully, what particular part of the body d chloroform injuriously affect when there is danger? Th just the point that the various Commissions have attem to settle. In the Scotch schools, more especially that Edinburgh, it has been taught that the great danger chloroform was in failure of respiration; meaning by the that the danger-signal of chloroform was the stoppage irregularity of the breathing. As a corollary to this bel it was considered that the heart was only affected at the breathing had become interfered with; that, in fa the respiration stopping, the blood was not oxygenate so the heart stopped beating. This was the teaching: the great Edinburgh surgeon, Syme. The English ari especially the London) teaching was almost direct opposed to this. It was taught, and is still taught in the London schools, that the great danger from chloroform arose from its effect on the heart, which stopped bearing before the respiration ceased. Which, then, of these t doctrines is true, or are both true?

The decision of this question is, as we have stated, one of vast importance; but it must be remembered that, whichever is right, the administrator of anaesthetics always pays attention to both the beating of the heart and the regularity of the respiration. Surgeon-Major Lawrie, one of the prominent members of the Hyderabad ChlorotorTa Commission, says that "it is possible to avert all risk to the heart by devoting the entire attention to the respirating during chloroform administration." Medical opinion f England, both of that of experts (professional anesthet and of the general profession, is distinctly opposed to his view; and the administrator who does not attend to the pulse, as well as to the breathing, is certainly neglecting one of the main paths by which Nature shows us what going on inside the organism.

From the statement of Surgeon-Major Lawrie jus quoted, it will be seen that the Hyderabad Chlorofor Commission came to the conclusion that the danger tr the administration arose, not from the heart, but from the respiration. This view was strongly combated in our con temporary, the Lancet. The importance of the questio led the Nizam of Hyderabad to obtain the services of scientific medical man from England to go out to India and attempt to settle the question. Dr. Lauder Brunton, F.R.S., consented to go; and, well known as he is for 15 life-long devotion to the experimental investigation action of remedies and their practical application, considered probable that his aid in the research wo lead to interesting and important results. From be somewhat scanty news of the results which have bee telegraphed to England, it seems likely that the invest gation now progressing at Hyderabad will tend to revolutionize existing views as to the action of chlorotom

of the

it was

Dr. Brunton's views as regards the dangers of chlore form before he left England were clearly expressed in his well-known" Text-book of Pharmacology." In it he s that "the dangers resulting from the employment

1

hloroform are death by stoppage of respiration and 4th by stoppage of the heart;" he lays as much stress a the effect on the heart as on the respiration, and he roceeds to affirm that too strong chloroform vapour y very quickly paralyze the heart. This view is, inred, similar to the one we have already mentioned as ught in the London schools of medicine. It is also til known that death may occur soon after chloroform 25 begun to be administered, from the heart being ected. If the operation is begun too soon, fainting rom pain may supervene, and a fatal result occur: this as always been strongly insisted upon by Dr. Brunton. surgeon-Major Lawrie says that in such cases it is not chloroform that acts on the heart, but simply that Gere is fatal syncope or fainting.

From the large number of experiments on animals which Dr. Brunton has performed in India, in conjuncon with the Hyderabad Commission and a medical delegate of the Indian Government, it appears that the danger from chloroform is asphyxia or an overdose;" here is none whatever from the heart direct. This stateTent is a distinct reversal of the view generally held in England. It means that chloroform causes a fatal result by affecting the respiration or by too much being taken into the system and affecting the brain; and that there 5 no direct paralysis of the heart from the chloroform. | A perfectly impartial opinion cannot, however, be formed from the scanty records of the investigation which have en as yet received in England. We must wait for fuller details of the experiments before a final judgment can be passed.

It is well, however, to point out that the prevailing view England has been founded, not only on experiments on the lower animals, but also on the extended clinical observation of two generations of medical men. Clinical observation is not so accurate or so lucid as that of direct experiment, but it has its value, and one by no means to * despised in a case where it is so extensive, and directed to a subject of such great importance, not only to the medical profession, but to the general public, as the question of the administration of chloroform.

IN

ON THE CAVENDISH EXPERIMENT. N the last number of the Proceedings of the Royal Society (vol. xlvi. p. 253), I have given an account of the improvements that I have made in the apparatus of Cavendish for measuring the constant of gravitation. As the principles and some of the details there set out apply very generally to other experiments where extremely minute forces have to be measured, it is possible that an abstract of this paper may be of sufficient interest to find a place in the columns of NATURE.

In the original experiment of Cavendish (Phil. Trans., 1798, p. 469), as is well known, a pair of small masses, (Fig. 1), carried at the two ends of a very long but light torsion rod, are attracted towards a pair of large masses, M M, thus deflecting the arm until the torsion of the suspending wire gives rise to a moment equal to that due to the attraction. The large masses are then placed on the other side of the small ones, as shown by the dotted circles, and the new position of rest of the torsion arm is determined. Half the angle between the two positions of rest is the deflection produced by the attracting masses. The actual force which must be applied to the balls to produce this deflection, can be directly determined in dynamical units when the period of oscillahub and the dimensions and masses of the moving parts are known. In the original experiment of Cavendish, the arm is 6 feet long, the little masses are balls of lead suches in diameter, and large ones are lead balls I foot diameter. Since the attraction of the whole earth on the smaller balls only produces their weight, i.e. the force

would produce a definite deflection against the torsion of his suspending wire.

These measures were repeated by Reich (Comptes rendus, 1837, p. 697), and then by Baily (Phil. Mag., 1842, vol. xxi. p. 111), who did not in any important particular improve upon the apparatus of Cavendish, except in the use of a mirror for observing the movements of the beam.

Cornu and Baille (Comptes rendus, vol. lxxvi. p. 954, vol. lxxxvi. pp. 571, 699, 1001) have modified the apparatus with satisfactory results. In the first place they have reduced the dimensions of all the parts to about onequarter of the original amount. Their beam, an aluminium tube, is only metre long, and it carries at its ends masses of pound each, instead of about 2 pounds, as used by Cavendish. This reduction of the dimensions to about one-quarter of those used previously is considered by them to be one of the advantages of their apparatus, because, as they say, in apparatus geometrically similar, if the period of oscillation is unchanged, the sensibility is independent of the mass of the suspended balls, and is inversely as the linear dimensions. I do not quite follow this, because, as I shall show, if all the dimensions are increased or diminished together, the sensibility will be unchanged. If only the length of the beam is altered and the positions of the large attracting masses, so that they remain opposite to, and the same distance from, the ends of the beam, then the sensibility is inversely as the length. This mistake-for mistake it surely is-is repeated in Jamin's "Cours de Physique," tome iv. ed. iv. p. 18, where, moreover, it is emphasized by being printed in italics.

The other improvements introduced by Cornu and

Baille are the use of mercury for the attracting masses which can be drawn from one pair of vessels to the other by the observer without his coming near the apparatus, the use of a metal case connected with the earth to prevent electrical disturbances, and the electrical registration of the movements of the index on the scale, which they placed 560 centimetres from the mirror.

The great difficulty that has been met with has been the perpetual shifting of the position of rest, due partly to the imperfect elasticity or fatigue of the torsion wires, but chiefly, as Cavendish proved experimentally, to the enormous effects of air-currents set up by temperature differences in the box, which, with large apparatus, it is impossible to prevent. In every case the power of observing was in excess of the constancy of the effect actually produced. The observations of Cornu are the only ones which are comparable in accuracy with other physical measurements, and these, as far as the few figures given enable one to judge, show a very remarkable agreement between values obtained for the same quantity from time to time.

Soon after I had made quartz fibres, and found their value for producing a very small and constant torsion, I thought that it might be possible to apply them to the Cavendish apparatus with advantage. Prof. Tyndall, in a letter to a neighbour, expressed the conviction that it would be possible to make a much smaller apparatus in which the torsion should be produced by a quartz fibre. The result of an examination of the theory of the instru ment shows that very small apparatus ought practically to work, but that in many particulars there is an advantage in departing from the arrangement which has always been employed, conclusions which experiment has fully confirmed.

As I have already stated, the sensibility of the apparatus is, if the period of oscillation is always the same, independent of its linear dimensions. Thus, if there are two instruments in which all the dimensions of one are n times the corresponding dimensions of the other, the moment of inertia of the beam and its appendages will be as n: I, and, therefore, the torsion also must be as no: 1. The attracting masses, both fixed and movable, will be as n3: 1, and their distance apart as n: 1. Therefore, the attraction will be as no/no or n1: 1, and this is acting on an arm n times as long in the large instrument as in the small; therefore the moment will be as n3: 1; that is, in the same proportion as the torsion, and so the angle of deflection is unchanged.

If, however, the length of the beam only is changed, and the attracting masses are moved until they are opposite to, and a fixed distance from, the ends of the beam, then the moment of inertia will be altered in the ration: 1, while the corresponding moment will only change in the ratio of n: I; and thus there is an advantage in reducing the length of the beam until one of two things happens: either it is difficult to find a sufficiently fine torsion thread that will safely carry the beam and produce the required period-and this, I believe, has up to the present time prevented the use of a beam less than metre in length-or else, when the length becomes nearly equal to the diameter of the attracting balls, they then act with such an increasing effect on the opposite suspended balls, so as to tend to deflect the beam in the opposite direction, that the balance of effect begins to fall short of that which would be due to the reduced length if the opposite ball did not interfere. Let this shortening process be continued until the line joining the centres of the masses M M makes an angle of 45° with the line mm; then, without further moving the masses M M, a still greater degree of sensibility can be obtained, provided the period remains unaltered, by reducing the length of the beam mm to half its amount, so that the distance between the centres of M M is 2√2 times the new length mm, at which point a maximum is reached.

It might be urged against this argument that a dif culty would arise in finding a torsion fibre that woul give to a very short beam, loaded with balls that it w... safely carry, a period as great as five or ten minutes, ar until quartz fibres existed there would have been a dir culty in using a beam much less than a foot long, b it is now possible to hang one only half an inch lo and weighing from twenty to thirty grains by a fibre n more than a foot in length, so as to have a period of ti minutes. If the moment of inertia of the heaviest beam a certain length that a fibre will safely carry is so small that the period is too rapid, then the defect can be remedi by reducing the weight, for then a finer fibre can be use and since the torsion varies approximately as the squar of the strength (not exactly, because fine fibres cam heavier weights in proportion), the torsion will be reduce in a higher ratio, and so by making the suspended par light enough, any slowness that may be required may be provided.

Practically, it is not convenient to use fibres much less than one ten-thousandth of an inch in diameter, and these have a torsion 10,000 times less than that of ordinary spun glass. A fibre one five-thousandth of an inch in diameter will carry a little over thirty grains.

Fur

Since with such small apparatus as I am now using :: is easy to provide attracting masses which are very large in proportion to the length of the beam, while with larg apparatus comparatively small masses must be made use of owing to the impossibility of dealing with balls of lead of great size, it is clear that much greater deflections can be produced with small than with large apparatus. instance, to get the same effect in the same time from an instrument with a 6-foot beam that I get from one in which the beam is five-eighths of an inch long, and the attracting balls are 2 inches in diameter, it would be necessary to provide and deal with a pair of balls each 25 feet in diameter, and weighing 730 tons instead of about 1 pound apiece. There is the further advantage in small apparatus that if for any reason the greates possible effect is desired, attracting balls of gold would not be entirely unattainable, while such small masses as two piles of sovereigns could be used where qualitative effects only were to be shown. Owing to its strongly magnetic qualities, platinum is unsuited for experiments of this kind.

By far the greatest advantage that is met with in small apparatus is the perfect uniformity of temperature whi is easily obtained, whereas, with apparatus of large size. this alone makes really accurate work next to impossible The construction to which this inquiry has led me, 115 which will be described later, is especially suitable te maintaining a uniform temperature in that part of the instrument in which the beam and mirror are suspended

With such small beams as I am now using it is much more convenient to replace the long thin box generally employed to protect the beam from disturbance by a vertical tube of circular section, in which the beam with its mirror can revolve freely. This has the further alvantage that, if the beam is hung centrally, the attraction of the tube produces no effect, and the troublesome and approximate calculations which have been necessary to find the effect of the box are no longer required. The attracting weights, which must be outside the tube, must be made to take alternately positions on the two sides of the beam, so as to deflect it first in one direction and then in the other. For this purpose they are most conveniently fastened to the inside of a larger metal tube. which can be made to revolve on an axis coincident with the axis of the smaller tube. There are obviously two planes, one containing and one at right angles to the beam, in which the centres of the attracting balls will he when they produce no deflection. At some intermediate position the deflection will be a maximum. Now, it i a matter of some importance to choose this maximum

position for the attracting masses, because, in showing the experiment to an audience, the largest effect should be obtained that the instrument is capable of producing; while in exact measures of the constant of gravitation this position has the further advantage that the only measurement which there is any difficulty in making, viz. the angle between the line joining the large masses and the ne joining the small, which may be called the azimuth of the instrument, becomes of little consequence under these circumstances. In the ordinary arrangement the slightest uncertainty in this angle will produce a relatively large uncertainty in the result. I have already stated that if an angle of 45° is chosen, the distance between the centres of the large balls should be 2 √2 times the length of the beam, and the converse of course is true. As it would not be possible at this distance to employ attracting balls with a diameter much more than one and a half times the length of the beam, and as balls much larger than this are just as easily made and used, I have found by calculation what are the best positions when the centres of the attracting balls are any distance apart.

If the effect on the nearer ball only is considered, then it is easy to find the best position for any distance of the attracting mass from the axis of motion. Let P (Fig. 2) be the centre of the attracting ball, N that of the nearer

Now, as the size of the attracting masses M M is increased, or, as is then necessarily the case, as the distance of their centres from the axis increases, their relative action on the small masses mm at the opposite ends of the beam increases, and so but a small fraction of the advantage is obtained, which the large balls would give if they acted only upon the small balls on their own side. For instance, if the distance between the centres of M M is five times the length of the beam, the moment due to the attraction on the opposite small balls is nearly half As great as that on the near balls, so that the actual sensibility is only a little more than half that which would be obtained if the cross action could be prevented.

I have practically overcome this difficulty by arranging

the two sides of the apparatus at different levels. Each large mass is at or near the same level as the neighbouring small one, but one pair is removed from the level of the other by about the diameter of the large masses which in the apparatus figured below is nearly five times as great as the distance in plan between the two small masses. In order to realize more fully the effect of a variety of arrangements, I have, for my own satisfaction, calculated the values of the deflecting forces in an instrument in which the distance between the centres of the attracting balls is five times the length of the beam, for every azimuth and for differences of levels of o, 1, 2, 3, 4, and 5 times the length of the beam.

The result of the calculation is illustrated by a series of curves in the original paper. The main result, however, is this.

In the particular case which I have chosen for the instrument, i e. where the distance between the centres of M M and the axis, and the difference of level between the two sides are both five times the length of the beam, as seen in plan, and where the diameter of the large masses is 64 times the length of the beam, the angle of deflection becomes 187 times as great as the corresponding angle in the apparatus of Cavendish, provided that the large masses are made of material of the same density in the two cases and the periods of oscillation are the same.

Having now found that with apparatus no bigger than an ordinary galvanometer it should be possible to make an instrument far more sensitive than the large apparatus in use heretofore, it is necessary to show that such a piece of apparatus will practically work, and that it is not liable to be disturbed by the causes which in large apparatus have been found to give so much trouble.

I have made two instruments, of which I shall only describe the second, as that is better than the first, both in design and in its behaviour.

The construction of this is made clear by Fig. 3. To a brass base provided with levelling screws is fixed the vertical brass tube t, which forms the chamber in which the small masses ab are suspended by a quartz fibre from a pin at the upper end. These little masses are cylinders of pure lead 11'3 millimetres long and 3 millimetres in diameter, and the vertical distance between their centres is 50.8 millimetres. They are held by light brass arms to a very light taper tube of glass, so that their axes are 6.5 millimetres from the axis of motion. The mirror m, which is 127 millimetres in diameter, plane, and of unusual accuracy, is fastened to the upper end of the glass tube by the smallest quantity of shellac varnish. Both the mirror and the plate-glass window which covers an opening in the tube were examined, and afterwards fixed with the refracting edge of each horizontal, so that the slight but very evident want of parallelism between their faces should not interfere with the definition of the divisions of the scale. The large masses M M are two cylinders of lead 508 millimetres in diameter, and of the same length. They are fastened by screws to the inside of a brass tube, the outline of which is dotted in the figure, which rests on the turned shoulder of the base, so that it may be twisted without shake through any angle. Stops (not shown in the figure) are screwed to the base, so that the actual angle turned through shall be lid made in two halves covers in the outer tube, and that which produces the maximum deflection. A brass serves to maintain a very perfect uniformity of temperature in the inner tube. Neither the masses M M, nor the lid, touch the inner tube. The period of oscillation is 160 seconds.

With this apparatus placed in an ordinary room with

I Cylinders were employed instead of spheres, because they are more easily made and held, and because spheres have no advantage except when absolute calculations have to be made. Also the verticai distance ab was for convenience made only about four times the length ab in plan.