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in the moving matter. This means

a moving force mann has suggested that we are to look for the explanation -(V,/,)oC But if there is compression, c, probably in the mutual action between the molecules and the always varies intrinsically as well.

æthereal medium which surrounds them. I am afraid, It will be found that the omission of the auxiliary h however, that if we call in the help of this medium, we has the result of complicating instead of simplifying the shall only increase the calculated specific heat, which is force formulæ. Similarly the omission of e complicates already too great."') It seemed to me, however, that the them. Now the use of e is founded upon the idea that difficulty was fully met by the numerical results arrived at the electric polarisation is produced by a separation of in chapter ix. of my book. ions under the action of E, for E, is the moving force on Suppose, to make the point at issue as definite as a moving unit electric charge. Analogously in, is the possible, we take a sample of air from the atmosphere, moving force on a moving unit magnetic charge or say at 15° C. Almost all the energy of this gas will be magneton. If there are really no such things, the inter- | assignable to five degrees of freedom-so far as we know, pretation must be made equivalent in other terms. But three of translation and two of rotation. Let us surround the categorical imperative is not easily to be overcome. this gas by an imaginary perfectly reflecting boundary.

The application to plane waves I described in a recent The total energy of matter and æther inside this enclosure letter (NATURE, March 9) will be found to harmonise with will remain unaltered through all time, but this total the above in the special case.

energy may be divided conveniently into two parts :But a correction is needed. In the estimation of the (1) The energy of the five degrees of freedom, say A. moving force on “ glass " receiving radiation, the assump- (2) The energy of the remaining degrees of freedom of tion was made that the electric and magnetic energies in the matter plus the energy of the æther, say B. the transmitted wave were equal. So the result is strictly As Lord Rayleigh insists, the system is now a limited by that condition. The conditions E=wB and servative system, so that according to the law of equiU=T are not coextensive in general, though satisfied partition, the total energy A+B is, in the final state of together in Lorentz's case. When U not =T, we have the gas, divided in the ratio instead of (8), p. 439,

A: B=5:00

(1) Div p.0P,w=w(T,-U,),

whereas observation seems to suggest that the ratio ought and the rate of loss of electromagnetic energy is

to retain its initial value 2uH,H,u+(w – u)(T,-U).

A: B=5:0

(2) Now this is zero when e=0, or the polarisation is pro- This I fully admit, but a further point, which I tried to portional to the electric force. The question is raised how bring out in the chapter already mentioned, is that the to discriminate, according to the data stated above, between transition from the ratio (2) to the ratio (1) is very slow cases of loss of energy and no loss. To answer this ques

--if my calculations are accurate, millions of years would tion, let e and n in the above be unstated in form ; else hardly suffice for any perceptible change-so that, although the same. Then, instead of (4), the activity equation (1) may be the true final ratio, it is quite impossible to will be

obtain experimental evidence of it.

If the sample of gas were initially at a much higher - OW=U + 1 + {JE?(06/06) + ...} +(999+1,u) – (eJ, +1G,), (5) temperature than we have supposed, the transition would where w is as in (4), whilst t, and t, are the forces

undoubtedly be much more rapid ; but even here we could derived from the stresses specified (not the same as F, and

not hope for experimental verification. For the assumed F.), and ... G, are the electric and magnetic polarisation boundary; impervious to all forms of energy and itself Currents, thus, =0+ Von, &c. It follows that it is possessing none, cannot be realised in practice, and as

soon as the energy of the enclosed æther becomes appreciupon e and h that the loss of energy depends in plane able, the imperfections of our apparatus would become of waves, when u and q constant. For the stresses reduce to longitudinal pressures, so that by line integration

paramount importance in determining the sequence of

J. H. JEANS. along a tube of energy flux we get (eli +1G = (U+T).

(6) Growth of a Wave-group when the Group.velocity is

Negative. Thus, when a pulse enters moving glass from stationary ether, the rate of loss of energy is 3(-e).). If e is zero,

The following may be of interest in connection with the so is the loss, as in the special case above. There is also recent discussion on the flow of energy in such cases. agreement with the calculated loss in the other case. Let the energy of an element of a linearly arranged That the moving force on the glass should be controlled mechanical system be by e is remarkable, for it is merely the small difference between the electric force on a fixed and a moving unit

{(dưyldxdt)? + y}dx/2. charge. The theory is not final, of course. If the electro- Such a system can be approximately realised by taking magnetics of the ether and matter could be made very a bicycle chain, loading it so that the radius of gyration simple, it would be a fine thing ; but it does not seem of each link has the same large value, and suspending it probable.

OLIVER HEAVISIDE. by equal threads attached to each link so that the chain April 5.

is horizontal and the axes of the links vertical. By the principle of least action we immediately find the equation

of motion to be d'y dx’dt = y. A simple harmonic wave The Dynamical Theory of Gases.

is given by y=sin (pt - x'p). The group velocity is -p, In a letter to NATURE (April 13) Lord Rayleigh makes a

and is negative. Let such a system, extending from x=0 criticism on my suggested explanation of the well known

to x=0, be at rest in its position of equilibrium at time difficulty connected with the specific heats of a gas. He t=0, and then let the point x=o be moved so that its posiconsiders a gas bounded by a perfectly reflecting enclosure,

tion at any subsequent time is given by y=-cost. and says " the only effect of the appeal to the æther is to

By application of the usual method vià Fourier's inbring in an infinitude of new modes of vibration, each of tegral, the motion of the system is found to be given by which, according to the law (of equipartition), should have

either of the equivalent formula its full share of the total energy. The apparent difficulty was before my mind when

y=3( - 1)"(11x)"+"Jgn +32 (1x), writing my book. Indeed, as Lord Rayleigh remarks, something of the kind had already been indicated by Max

y=I - cos(1 + x) – 1 +31 – 1)"(x/t)") 22 11x), well. (I think the passage to which Lord Rayleigh refers where the J's are Bessel's functions and the summations will be found in the “ Coll. Works," ii., p. 433 :-“ Boltz- | extend from n=0 n=0. There are some doubtsul

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Possibly, in a few instances, the ridges on the their base, which was published in the third volume hill-slopes may be due to outcropping strata, and of the Indian Memoirs. This contains a sketch of others might suggest terrace-cultivation; but there the history of the Himalayas which has been generally seems ample evidence for the view taken that accepted ever since. Neolithic cattle-tracks have survived to this day After returning to the survey in 1862 (he always around certain of our most imposing

protested that he really had remained a member of Failing large-scale maps, a sketch-plan of the the staff throughout), he examined in successive years earthworks noticed would have made the description the greater part of northern India. Various tracts even more illuminating; but the only matters of com- of the Himalayas from the Punjab to Assam, the plaint are that the book is all too short, and that the Assam valley and the hill ranges south of it, and, in paper selected to throw up the detail of the photo- the Peninsula, Rajputana, Nimar, the Nerbudda graphs is as chalky as the Downs they illustrate so valley and Satpura ranges, Bundelkhand, South pleasantly.

Rewah, Chhatisgarh and Sambalpur, Chota Nagpore,

Hazaribagh, and Behar were visited and reported HENRY BENEDICT MEDLICOTT, F.R.S.

upon in turn.

Dr. Oldham retired in 1876, and Mr. Medlicott ON N April 6 there passed away one of the few succeeded him as superintendent, a title subsequently

survivors amongst the small body of men who changed to director of the survey. The first work laid the foundations of Indian geology. Despite undertaken by him as superintendent was a general much excellent work, chiefly by non-professional men,

account of Indian geology. This had long been very little was really known of the geology of India, urgent, and would probably have been written by Dr. and especially of Peninsular India, before the middle Oidham but for failing health. The “ Manual of the of the nineteenth century, and

instance Geology of India " was published in 1879, and a very amongst many, the Vindhyans, now believed to be large portion, including the account of the Azoic Archæan, were still classed with Gondwana Permo- rocks from gneiss to Vindhyans (which between Carboniferous strata, and both were regarded as of them cover the greater part of the Indian peninsula), Jurassic age.

A comparison of Dr. Carter's and of the geology of the Himalayas and sub-HimaSummary of the Geology of India between the layas, in fact, nearly half the entire work, was Ganges, the Indus and Cape Comorin,” published in

written by Mr. Medlicott himself. In many ways a 1853, with the “ Manual of the Geology of India," great impulse was given to survey work by the new issued in 1879, will show the great improvement that superintendent. As regards publication alone, the took place in the meantime in our knowledge of the

volumes of the Records from 1877 are doubled in country.

bulk when compared with previous issues, and these In this change none had a larger share than Henry volumes, containing accounts of recent geological Benedict Medlicott. Born

in Loughrea, county observations, both economical and scientific, represent Galway, he was the second of three sons of the Rev. the actual field work of the survey to a larger extent Samuel Medlicott, rector of Loughrea, and of Char: than the longer memoirs and palæontologia. lotte, the daughter of Colonel H. B. Dolphin, C.B. Throughout his career as head of the survey Mr. All three sons were men of great intellectual capacity Medlicott adopted a most liberal policy of publication. and of marked originality. The eldest, J. G. Medli. He allowed his staff to report on their own work cott, became a member of the Geological Survey of freely, and whilst assisting them in every way, both India before his brother joined; he was subsequently in the field and in the study, he never took any of in the Indian Educational Service, and died in 1866. the credit of their work. Not only did he welcome The third brother, Samuel, was 'a clergyman, who reports from the geologists of the survey, but he has also been dead several years. The subject of the published, whenever possible, contributions from inpresent memoir Dublin, and, after taking his degree, was for a short valuable assistance of the late General McMahon, the

was educated at Trinity College, dependent observers. In this manner he secured the time on the staff, first of the Irish, then of the whole of whose most important observations on the English Geological Survey. In the spring of 1853 physical history of the Himalayas appeared in the he joined the Geological Survey of India under the Records of the Geological Survey of India. late Dr. Thomas Oldham, but was almost immedi- Modest and retiring, he was nevertheless a man of ately appointed professor of geology at the Roorkee high courage and independence. One trait of this College of Civil Engineering, an appointment which was shown in the Indian Mutiny, when, with one he held until 1862, when, on some additions being companion, despite the mutiny of the guard that made to the staff, he re-joined the Geological Survey should have accompanied them, he saved the lives of of India, and was made deputy superintendent for a Christian family who had fallen into the hands of Bengal.

the rebels, a most gallant action, the account of which But during his tenure of the Roorkee post he spent is due to Colonel Baird Smith, the head of Roorkee part of the year surveying for the Geological Survey, College and the commanding officer. After retiring and in his first season's work he and his brother from the Indian Survey in 1887, he lived very quietly made a primary step towards the elucidation of at Clifton, devoting himself to philosophical problems. Indian geological history by separating the ancient He published a couple of short pamphlets on Vindhyans north of the Son and Nerbudda Rivers “ Agnosticism and Faith" in 1888, and on "The from the Indian Coal-measures and their allies to the Evolution of Mind in Man," but a larger work on southward. In subsequent years, whilst his brother which he was engaged is, it must be feared, incommapped the last named strata, he surveyed the older plete. A strain caused by bicycling led to serious Vindhyans and their associates, and to him we owe heart symptoms some years ago, and although a parour first recognition of the Bijawur and other ancient tial recovery was made, a relapse about a year since rocks between the old gneissic formation and the reduced him so much that it was not surprising to Vindhyans. In other years he explored the Hima- hear that he passed quietly away on April 6. whilst layas, and the ranges at their base, between the seated in his study. Ganges and the Ravi, and he drew up the descrip- Mr. Medlicott became a Fellow of the Geological tion of the older unfossiliferous beds of the moun- Society as long since as 1856, and in 1888, on his tains, and of the Tertiary and other strata fringing retirement from India, he received the Wollaston

a

orbit. The deviation amounts to but 3°, and its plane of proteids-have, on account of their complexity, critical rotation has therefore shifted through 177o.

temperatures of decomposition which lie very close to the The explanation of the retrograde rotation of Phæbe is normal temperature of the earth's surface. now also clear. Phæbe, the first-born of Saturn's If, now, by some means we proceed to add on atoms numerous retinue, came into being while the planet itself to such a molecule so as to make it more and more comstill retained its original plane of rotation, that is, while plex, we would steadily lower its critical temperature of it was still revolving in a retrograde direction. Before decomposition, and by adding on a suitable kind and lapetus, Saturn's second satellite, reckoning from without number of atoms we could reduce the critical temperature inwards, was created, the mighty tides acting upon the and pressure of the compound until they coincided with planet in its then diffuse condition had shifted its plane of the normal temperatures and pressures which hold upon rotation more than 90°. Two forces then acted on the the earth's surface. Such a compound would be possessed plane of the orbit of the new satellite, one from the sun of an extraordinary sensitiveness to external influences on tending to bring the orbit into the plane of the orbit of account of the sharpness of the constants called above the Saturn, the other from Saturn tending to bring the orbit critical temperature and pressure of the compound. The of the satellite into the plane of the equator of its primary. slightest increase of temperature or decrease of pressure At first both forces tended to produce the same result, would serve to throw it into a condition of rapid chemical namely, to diminish the angle of inclination of the plane decomposition, whereas a slight increase of pressure and of the orbit of the satellite. They are now pulling in decrease of temperature would cause it to cease to deopposite directions, as is the case with our own moon, the compose. Even did we maintain the external temperature inclination of the orbit of lapetus, 19°, being less than and pressure exactly at the critical temperature and that of the equatorial plane of its primary.

pressure of the compound, nevertheless the external imThe inner satellites of Saturn are more powerfully pulses which are continuously pervading all space in the affected by the equatorial expansion of the planet than by neighbourhood of the solar system, beating intermittently the action of the sun, the planes of their orbits, 270, coin- upon the sensitive substance, would be sufficient to throw ciding nearly with the plane of the planet's equator. it into a series of rapidly alternating states of decomposi

WILLIAM H. PICKERING.

tion and repose. Harvard Observatory, Cambridge, Mass., U.S.A.

I suggest that the temperature range of animal life is probably nothing more or less than the range of the critical

temperatures of decomposition of a series of certain very Have Chemical Compounds a Definite Critical

complex carbon compounds which are grouped together

under the name “ protoplasm, " the external pressure of Temperature and Pressure of Decomposition ?

the atmosphere coinciding roughly with their critical So far nobody seems to have considered the question pressures of decomposition. In fact, I suggest that just whether to every chemical compound there exists a definite as a tuning-fork is set into motion by vibrations of a critical temperature and pressure of decomposition. Yet certain definite frequency and by no others, so living I think the following considerations show that such con- matter is so constructed as to respond continuously to the stants probably do exist. Suppose we place a given com- incessant minute fluctuations in the external conditions pound (say Caco,) in a closed cylinder and subject it to which hold upon the earth, the state of response being a continually increasing temperature, keeping the pressure what is known as life. The temperature of animal life constant by means of a weighted piston. Then at keeps remarkably constant, as it should do .on our supcertain definite temperature range the compound will begin position, a temperature too high exceeding the critical to decompose. Suppose, now, we increase the pressure temperature of decomposition of living matter and sufficiently; then the decomposition ceases, and the sub- destroying its structure, while a temperature too low causes stance can now bear a higher temperature than before it to cease to decompose, and the living matter becomes without decomposition.

inactive.

GEOFFREY Martin. Proceeding in this way, it is, I think, obvious from the University of Kiel, April 4. finite nature of the mass of the atoms, and from the limited intensity of the forces holding them together in

[The writer of the above will see his “ suggestion " disthe molecule, that ultimately at definite finite

cussed in Lockyer's “Inorganic Evolution, book iii.temperature the external forces tending to drive the atoms

ED. NATURE.] apart will become equal to the maximum internal forces that the atoms can exert on each other in the molecule. It therefore follows that above a certain definite tempera

Experiment on Pressure due to Waves. ture, depending upon the nature of the molecule, no I

seen both in the Physikalische Zeitschrift pressure, however great, can prevent the substance from

(January) and in the Physical Review (February) an completely decomposing. This temperature and pressure, account of an experiment by Prof. R. W. Wood to demonabove which a compound is incapable of existing, we will strate the pressure due to waves, and which he suggests call the critical temperature and pressure of decomposition

lecture demonstration of the effect observed by of the compound. The critical temperature and pressure of Lebedeff and by Nichols and Hull. The same experiment decomposition would therefore be completely analogous to is quoted by Prof. Poynting in his address on this subject the critical temperature of liquefaction of a compound- to the Physical Society of London (Phil. Mag., April). I only in the latter case we are dealing with the temperature venture to suggest that the experiment, which consists in whereat a certain molecular condition of existence dis- setting a small windmill in motion by means of Leyden appears, and in the former case with the temperature jar discharges maintained by a transformer, will bear a whereat a certain atomic condition of existence disappears. different explanation. It was shown long ago (1793) by

Since atoms are a very much more finely divided form Kinnersley, of Philadelphia, in his “ Electrical Thermoof matter than molecules, it is clear that the critical meter, that a jar discharge produces in air a violent extemperature of decomposition of a compound must be a plosive effect, which we should now explain by the revery much sharper and clear-cut constant than its critical pulsion between constituents of the current in opposite temperature of liquefaction. The critical temperature and phase to one another. The repulsive force may be very pressure of even very unstable compounds is usually very great. I think it is this explosive effect that Prof. Wood high, provided there exist but a few atoms in the molecule. shows in the experiment, and not the pressure due to reflecFor example, Auci,, ozone, and the oxides of nitrogen, tion of a continuous train of waves. I do not think that although very unstable at ordinary temperatures, seem the suggestion is new, but it appears to me that the same capable of existing at very high temperatures. In general, cause may account for the disruption which occurs when the greater the number of atoms contained in the molecule lightning strikes a building, an instance of which is rethe lower the critical temperature of decomposition, as is corded in NATURE of April 13 (p. 565) in the displacement evident from the general observation that the more com- of some of the blocks of the small pyramid. plex a compound is the easier it is to decompose. Many

SIDNEY SKINNER. of the very complex carbon compounds—for example, the South-Western Polytechnic, Chelsea, April 15.

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TANTALUM.

for three days, and at the end of the time had only HE application of electricity to chemical problems of the drill was very much worn.

made a depression 0.25 mm. deep, while the diamond has again borne fruit in the isolation and pre- very probably lead to its being used for drills in place paration of tantalum. Dr. Werner von Bolton, of of the diamond. the firm of Siemens and Halske, published the results The metal melts between 2250° and 2300° The of his very interesting research upon the preparation atomic heat agrees with the law of Dulong and Petit, of tantalum in the Zeitschrift für Elektrochemie being 6.64. The specific gravity is 14.08.When two (January 20). Although the existence of tantalum electrodes of tantalum are placed in a bath of dilute was pointed out by Hatchett in 1801, it does not sulphuric acid, the tantalum becomes passive, and appear up to the present to have been prepared in even with an E.M.F. of 220 volts at the terminals the pure condition. Moissan, indeed, in 1902 pre- no current passes. When placed opposite an electrode pared the metal by reducing tantalic oxide (Ta,0,5) of platinum only one phase of an alternating current in the electric furnace. But the metal was extremely passes; it may thus be used for rectifying an alterhard and brittle, a property which Dr. Bolton now nating current in the same manner that aluminium shows only belongs to the impure product; Moissan's metal probably contained some carbide. Dr. Bolton In the form of wire, sheet or ingots, the metal is has succeeded in obtaining the metal by an electrical unacted upon by sulphuric, hydrochloric, or nitric and by a chemical method.

acid, and even by aqua regia.

Hydrofluoric acid reacts very
The Electrolytic Method.

slowly, unless the metal is in As is well known, Nernst found that when a thin

contact with platinum, for rod of magnesia (MgO) is heated to whiteness it example, in a platinum dish, becomes able to conduct the electric current, the

when it dissolves readily with magnesia being split up into its components, mag

evolution of hydrogen. Fused nesium and oxygen; the magnesium, however,

alkalis have no action upon it. immediately re-combines with oxygen, the process of

When made the kathode in electrolysis therefore becoming continuous. Other

an acid electrolyte it absorbs metallic oxides, such zirconium, ytterbium, hydrogen, which is only parthorium, calcium, and aluminium, &c., likewise be- tially given up,, even when have in a similar manner. If, now, a rod of mag

the metal is fused. The metal nesium is strongly heated in vacuum and the electric may be heated to red heat in current passed through it, the oxygen given off is so

the air without taking fire. dilute that re-combination does not take place, and

At
400o it
turns slightly

110 the rod becomes powdered.

Dr. Bolton, working yellow, at a low red heat it along somewhat similar lines, found that the coloured

turns blue, and finally beor lower oxides of vanadium, niobium (columbium),

comes coated with a white and tantalum will conduct the electric current with protective coating of the pentout the necessity of being heated to very high

oxide. It absorbs nitrogen at temperatures. Strange to say, the colourless

a white heat, and unites with higher oxides have not this property.

sulphur when melted with it

FIG 1.- View of Tantalom In order to prepare tantalum in this manner

under

fused potassium Lamp. Half-size linear. filament of the brown tantalum tetroxide (Ta,O) was

chloride. Tantalum appar-, prepared and fixed into an evacuated globe, which ently forms no amalgam with mercury, although it was connected with a vacuum pump, so that it'oxygen produces alloys with most other metals. When united was given off, on heating, it could be pumped out.

with i per cent. of carbon it becomes hard and brittle On passing a current through this filament, at first

and can no longer be drawn into wire. the two ends of the filament became white hot, and

As already stated, the original idea in working with then gradually the incandescence travelled along the

tantalum was to find a new material to be used for filament until the whole of it became incandescent.

incandescent electric lamps. The first experiments A large quantity of oxygen was given out, and the (columbium); the coloured or lower oxides of these

were tried with the oxides of vanadium and niobium filament, which at the commencement was brown, metals were found to conduct the current and to give became metallic grey.

The tantalum so obtained showed on analysis a purity of 99 per cent.

up their oxygen when thus heated in vacuum. Vanadium so obtained was found to melt at 1680°

and niobium at 1950°; but owing to these comparaThe Chemical Method.

tively low melting points they could not satisfactorily Details as to how the chemical method is carried be employed for electric lighting purposes. Tantalum, out are not given. Dr. Bolton simply says that the however, which melts between 2250° and 2300° has metal can be obtained by fusing a mixture of potas been successfully employed for this purpose by Messrs. sium tantalum fluoride with potassium by means of Siemens and Halske. the electric arc furnace in a vacuum. This method

Filaments of the metallic tantalum are fused into is a modification of that used by Berzelius in 1824.

a globe, which is then evacuated in the usual manner.

The first lamp was made with the usual bow-shaped Properties of the Metal.

filament, and required 0.58 ampere with a pressure

of 9 volts, giving 3 candle-power. It was then found One of the most remarkable properties of the metal that in order to produce a 22 candle-power lamp suitis its extreme ductility combined with extraordinary able to being placed on a 110-volt circuit more than hardness. The red-hot metal can readily be rolled 20 inches length of filament was required. The diffiinto sheets and foil, and easily drawn into wire. culty presented was to get this great length of filaWhen the sheet is again heated and hammered it ment conveniently into the ordinary sized globe. The becomes so extremely hard that it was found im- illustration (taken from the Electrical Magasine for possible, by means of a diamond drill, to bore a hole March) shows how the difficulty was got over. The through a sheet 1 mm. thick. The drill, rotating central support is a rod of glass, having a number of 5000 times to the minute, was worked day and night wires radiating from it to act as supports.

This

or

a

lamp gives 22 candle-power with an energy consump- such reservoirs might make us chary of crediting tion of 1.7 watt per candle-power, or about half that prehistoric man with such scientific methods. required by the ordinary incandescent lamp. The An exposed position innocent of springs was weight of a single filament is 0.022 gram, so that selected, and straw or some other non-conductor of i kilogram of metal would be sufficient for 45,000 heat spread over the hollowed surface. This was such lamps.

next covered with a thick layer of well puddled clay, Whether it will be possible to obtain sufficient which was closely strewn with stones.

The pond mineral to produce tantalum on a really large scale would gradually fill, and provide a constant supply remains to be seen, because if it is possible there of pure water, due to condensation during the night should be hardly an end to the usefulness of this of the warm, moist air from the ground on the metal, which possesses the properties ductility and surface of the cold clay. Evaporation during the day hardness in such an extraordinary degree, leaving is less rapid than this condensation, and the only entirely out of question its employment in electric danger is that the straw should be sodden by leakage. lamps.

F. MOLLWO Perkin. It is for this reason that springs or drainage from

higher ground are avoided, as running water would

cut into the clay crust. PRIMITIVE WATER-SUPPLY."

Some ponds of this kind, no doubt of very early and THE

E mighty earthworks that still crown so many perhaps of Neolithic date, may still be seen in working

of our hills fill the archæologist alike with order : others are of modern construction ; but to and wonder and despair-wonder that prehistoric man, from the ancient dew-ponds (or their sites) can somewith the most primitive tools, was equal to the task times be traced the hillside tracks along which the of raising them, and despair that so little can ever be known about them, despite the most laborious and costly excavation. Plenty of books, however, of the kind now under notice would do much to solve the mystery and increase our admiration for Neolithic man, for it is to the period before bronze was known in Britain that the authors assign the stupendous works of Cissbury and Chanctonbury on the South Downs.

This is an open-air book that gives life to the dry bones of archæology, and reads like the record of a well-spent holiday. A keen eye for country is one of the qualifications possessed by one or both the authors, and evidence of ramparts long since levelled is wrung from the very daisies as they grow. The construction of dew-ponds by the early inhabitants of Britain has often been glibly asserted, but few, if any, have fur- Fig. 1.- Cattle-ways leading down to Dew-pond at the North of Cissbury Ring.

Neolithic Dew.ponds and Cattle-ways.” nished such clear and circumstantial evidence as the authors of this short treatise. The water-supply herds were driven, one leading from the camp, or for the occupants of our huge prehistoric camps cattle-enclosure hard by, the watering-place, has always been somewhat of a mystery, and it another leading back, to avoid confusion on the road. has been suggested that they were only tem- These and other details as to guard houses and posts porary refuges, when the country was “ up,” so of observation are brought to notice in the that a permanent supply was not regarded as description of selected strongholds in ‘Sussex and necessity. But the watering of men and animals on Dorset; and verification, if, indeed, such is demanded, the scale indicated by the areas enclosed would be a must be sought on the spot by any who have doubts formidable task even for a day, and another explana- or rival theories. tion must be sought. The late General Pitt-Rivers, The banks, that enclosed pasture-areas sometimes for example, held that the water-level of the combes of vast extent, were no doubt stockaded against man was higher then than now, and streams would have and beast, and may be compared with the basebeen plentiful on the slopes; but, feeling the

court defences of the Norman burh; but the excavator inadequacy of this view, he also had recourse to the of Wansdyke had an alternative theory that such dew-pond' theory. To those familiar

with the banks were sometimes erected for driving game. process, this might seem an obvious expedient, but Incidentally, the authors discountenance the view that the interesting account given of the formation of the “camps," not to mention the outworks, were

ever efficiently manned. Their extent would 1 "Neolithic Dew-ponds and Cattle-ways." By A. J. Hubbard and G. Hubbard. Pp. x+69; illustrated. (London: Longmans, Green and Co.,

necessitate for this duty a vast number of fighting 1995.) Price 35. 61. net.

men within call.

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