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problems and exercises are likewise provided. The

LETTERS TO THE EDITOR. style of the author is attractive, and the course as a [The Editor does not hold himself responsible for opinions whole has great educational value; in fact, we know expressed by his correspondents. Neither can he undertake of no which presents the subject in a way to return, or to correspond with the writers of, rejected more suited to the natural capacities of the youthful manuscripts intended for this or any other part of NATURE. reader, or which is better adapted to impart a

No notice is taken of anonymous communications.] thorough knowledge of concrete geometry, and at the

Ionisation and Temperature. same line to develop the reasoning faculties in a The discourse by Prof. J. J. Thomson, published in legitimate manner.

SATURE of March 22 (vol. Ixxiii., p. 495), was of importThere is a chapter describing the vernier, sphero- ance from several points of view. The explanation of the meter, callipers, and the micrometer screw gauge,

method of ionisation which he suggests was of especial and also treating briefly of the mensuration of the

interest to myself, and I should be pleased if I might be simpler grometrical solids. There are selections of allowed to raise one query concerning it. recent examination papers, four-figure logarithms

Prof. Thomson does not regard the temperature of the und trigonometrical ratios, answers to numerical pro- indeed, never been shown that high temperature alone

gas as having any effect upon the ionisation. It has, blems, and a very useful general index.

would produce ionisation. On the other hand, is there any If a draughtsman were to criticise the book he

reason for supposing that ionisation by impact may not would probably say that in measuring and setting take place much more easily at high temperature than at uti lengths the scale should be directly applied with low, and that this is the explanation of the discharge out the intervention of dividers; that a line to be ac- observed by Prof. Thomson? That the gas in this case curately measured should have its ends clearly defined must have a very high temperature would seem exceedingly by short cross-lines; and that diagonal scales, being probable, for the amount of electrical energy lost in the of little or no practical use, are made rather too much discharge is very great when compared with the thermal of in the chapter devoted to them. But these are very capacity of the gas through which the discharge occurs. minor matters, and do not detract from the general Thus in one case when the discharge became luminous the vellence of the work. We know of no text-book

current was 0.045 ampere, the potential difference 50 volts,

the distance between the electrodes 5 mm., and the pressure oi elementary geometry which can be more

of the gas 0.01 mm. The dimensions of the tube are not fidently recommended to teachers, and none from given, but if we assume the volume of the gas to be 2 c.c., which students are likely to derive more profit. the residual gas to be atmospheric gas, and that the whole Les Procédés de Commande à Distance au Moyen de

electrical energy is used in heating the gas, we should l'Electricité. By Captain Régis Frilley. Pp. vii +

conclude that it would raise it 7.4 X 10' degrees. It is, of

course, not to be supposed that the temperature does reach 190. (Paris : Gauthier-Villars, 1906.) Price 3.50

any such value, but we have reason to believe that it francs.

reaches a very high temperature, and may it not be that THE problem considered in this volume is that of this has a very great effect upon the production of the communicating to a distant mechanism a movement ions?

C. D. CHILD. the magnitude, direction, and sense of which are de- Colgate University, Hamilton, N.Y., May 11. finite functions of those of a transmitting mechanism. The character of the movements which it is desired to

The average temperature of the gas when the discharge transmit varies very much in degree from the simplest

first became luminous was comparatively low; for example, of all (traction), in which the three “commands "

a fine platinum wire immersed in it did not become hot joruards, backwards, stop-are alone the orders to

enough to be visible. The figures quoted by Prof. Child be obeyed. The author classifies the different me

refer to the current after the luminous discharge had been

well established; the current when the transition from chanisms employed, not according to their complica- dark to luminous discharge took place was very much tion, but according to the methods that are charac. smaller, generally less than 10-s ampere. teristic of them. These form seven groups—(1) direct

J. J. THOMSON. action apparatus, (2) apparatus using relays, (3) apparatus employing rotating fields, (4) Wheatstone's

A Horizontal Rainbow. bridge devices, (5) apparatus based on the use of J'ai étudié récemment un arc-en-ciel horizontal qui se induction sparks, (6) escapements, (7) Hertzian waves. montrait à la surface d'un petit étang dans les premières The various devices that have been used from time heures de la matinée. On l'observait, comme celui dont to time are very clearly described under these head

Mr. W. R. M. Church a envoyé la description à NATURE ings with the aid of diagrams. In chapter viji. an

(April 26, p. 608), en tournant le dos au soleil ; et il disaccount is given of the commutating device of Lieu-paraissait quand la hauteur du soleil était de 44° environ. tenant-Colonel Rivals, by which the sending and re

Il avait la forme d'un arc d'ellipse dont un foyer se serait

trouvé à peu près dans l'ombre de la tête de l'observateur. ceiving instruments can be used as either in turn.

Ses caractéristiques étaient les mêmes que celles de l'arcAltogether the book forms a very useful and sug

en-ciel ordinaire : ouverture angulaire de 42° sur le bord gestive summary of this very important branch of

rouge, largeur de 2°, apparition à 53° (plus rare) d'un modern military practice.

second arc plus faible et plus large avec les couleurs Das Radium_und die radioactiven Stoffe. By Karl disposées dans l'ordre inverse, obscurité de l'espace compris

entre les deux arcs. Frhr. von Papius. Pp. viii + 90. (Berlin : Gustav

Tout invitait donc à chercher l'origine du phénomène Schmidt.) Price 2 marks.

dans des sphérules d'eau, qui ne pouvaient être que This book contains a semi-popular account of radio- répandues sur la surface calme. C'est effectivement ce active phenomena. The leading experimental facts qu'une étude attentive m'a fait découvrir. Les sphérules and the conclusions of their discoverers are described en question ont généralement quelques dixièmes de milliclearly enough, but with little in the way of sug

mètre de diamètre. Elles sont très nettement visibles quand gestive comment. The printing and illustrations are on se penche sur l'étang, mais la moindre agitation les fait good, but we notice a serious error in Fig. 10, which disparaître. Je les attribue à la rosée déposée à la surface suggests that the B-rays of radium, when deflected

de la nappe tranquille, laquelle est un peu grasse par suite by magnetic force, lie in the same plane as the poles végétaux dans ses eaux stagnantes. L'arc-en-ciel observé

de l'existence de nombreuses colonies d'animalcules et de of the defiecting magnet. The contrary is, of course, the fact, and such a mistake cannot but suggest du brouillard à l'état sphéroïdal sur la surface calme du

par Mr. Church me semble dû à la même cause : dépôt serious doubts as to the competence of the author's lac.

V. SCHAFFERS. general scientific knowledge.

R. J. S. Louvain (Belgium), rue des Récollets, 11.

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monolith enclosed within it was inclined, it is pos

sible that it was upright at that time. III.

“Dr. Stukeley's supposition was that it originally Boscawen-un, N. lat. 50° 5' 20''.

stood upright, and that somebody digging by it to

find treasure disturbed it.' My

“ On the north-east side there are two fallen stones day, when it was impossible to make any observ- which Dr. Borlase, in 1749, imagined to have formed ations. Mr. Horton Bolitho, who was with us, in- part of a cromlech. It is more probable that they troduced us to the tenant of Boscawen-noon—Mr. are the fragments of a second pillar which was placed Hannibal Rowe—who very kindly, in spite of the bad to the north-east of the centre, and as far from it as weather, took us to the circle and the stone cross to the existing one is. There are instances, I believe, the N.E. of it.

of two pillars occupying similar positions within a Lukis thus described this monument ? :

circle. One of the stones, that marked C in my " The enclosed ground on which this circle stands plan, on the eastern side of the ring was prostrate is uncultivated and heathy, and slopes gently to the in the doctor's time. south. Twenty years ago a hedge ran across it and " At a short distance to the south-east and southbisected the circle.

west there are cairns, which have been explored."

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“ This monument is composed of nineteen standing For this monument I have used the 6-inch map, as stones, and is of an oval form, the longer diameter 'the circle lies nearly at the centre, and all the outbeing 80 feet and the shorter 71 feet 6 inches. One standing stones are within its limits. The heights of the stones is a block of quartz 4 feet high, and the of the sky-line were measured by Mr. H. Bolitho at rest, which are of granite, vary from 2 feet 9 inches a subsequent visit with a miner's dial; the resulting to 4 feet 7 inches in height. On the west side there declinations have been calculated by Mr. Rolston. is a gap, whence it is probable that a stone has been A theodolite survey will doubtless revise some of removed. Within the area, 9 feet to the south-west

them :from the centre, is a tall monolith, 8 feet out of the

Marks ground, which inclines to the north-east, and is 3

1. F. Stone cross feet 3 inches out of the perpendicular.

N. 43 15 E.

+29 26

Capella \. 53 30 E.

Solstitial Sun “In 1594 Camden describes this monument 3. B. Blind Fiddler N. 54 consisting of nineteen stones, 12 feet from each 2 Large menhirs N. 06 50 E.

May sun 5. Stone cross

o (9) + 8 8 Pleiades

1430 other, with one much larger than the rest in the

(May) centre. It must have been much in the same con

S. 66 30 E.

November sun dition then as now. As he does not say that the

N. 83 30 W o(?) + 4 36


(September) i Continued from v l. lxxiii., p. 563.

I gather from a report which Mr. H. Bolitho has 9 “Prehistoric Stone Monuments of the British Isles : Cornwall," W.C. Lukis, p. 1.

been good enough to send me that modern hedges


2. P. fine menhir


sc E.

... 2 7

2 23
2 23
1 o

23 59
23 25
14 55

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N. -8

o E.

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6. Stone

o(?) -14 32

7. Stone


21 20 Dec.



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and farming operations have changed the conditions feet in diameter, and the whole monument is, in of the sight-lines, so that i and 3 are just invisible Lukis's opinion, the most interesting and remarkable from the circle. This is by no means the only case in the country. Surrounding the platform there is a in which the sighting stone has just been hidden ditch I feet wide, and beyond that a penannular over the brow of a hill and in which signals from an vallum about 10 feet in width. The peculiarity of observer on the brow itself have been suggested, or a the vallum is that it has three bastions situate on via sacra to the brow from the circle; there are many the north-east, north-west, and east sides. It is to monoliths in this direction which certainly never the north-east bastion that I wish to refer. belonged to the circle. From menhir P (No. 2) a Sighting from the huge monolith, which is now fine view is obtained from N. to S. through E., so prostrate but originally marked the centre of the that the Blind Fiddler and the two large menhirs, circle along a line bisecting the arc of this bastion, and almost the circle, are visible. The curious shapes we find that the azimuth of the sight-line is N. 25° E.; of 1 and 2 are noted, the east face vertical and the the angular elevation of the horizon from the 1-inch west boundary curved, like several sighting stones on Ordnance map appears to be about o° 22'. Thus we Dartmoor.

get in the same form as before :The circle itself has several peculiarities. In the

Alignment first place, as shown by Lukis, it is not circular, the

Centre of circle to centre of bastion

35° 1' N.

Capella 1250 B.C. diameters being about 85 and 65 feet; the minor axis runs through the pillar stone in the centre and the indicating that this alignment was formed for the ** fallen stones” of Dr. Borlase towards the “ stone

same purpose as that which dominated the erection cross " (which is no

of “ The Pipers. cross but a fine menhir) in Az. N. 43° 15' E. This would suggest that this was The Nine Maidens the original alignment in 2250 B.C., but against this

(lat. 50° 28' 20" N., is the fact that the two stones of the circle between

long. 4° 54' 35" W.) which the ' fallen stones" lie are more carefully In this monument we find a very different type from squared than the rest. It is true, however, that this those considered previously. might have been done afterwards,

2 and this

seems probable, for they are closer together than the other

It circle stones.

The one quartz stone occupies an 1° azimuth S. 66° W. It was obviously placed in a post of honour. As a matter of fact, from it the May sun was


SEALEVEL rise over the centre of the circle.

As there
both at Tregaseal
and Boscawen-un
alignments sug.
gesting the ob-
servation of the 1905AD. 20



summer solstice
sunrise, it is de- 1680BC 499


53 sirable here to

(onico STACHERCE) refer to the azi. Fig. 9.-Showing the azimuths at the present time and in 1680 B.C. at which the sun rose in Cornwall at the solstice, muths calcu.

with different elevations of the sky-line. These are shown at the side. lated. For this purpose Fig. 9 has been prepared, which shows these The Nine Maidens are simply 9 stones in a straight for lat. 500 both at the present day and at the date line 262 feet in length at the present day; possibly, of the restoration at Stonehenge.

as suggested by Lukis, it may have extended My readers should compare this with the table on originally to the monolith known as “ The Fiddler," p. 33, vol. lxxii., which gives the solstice sunrise con- / situated some 800 yards away in a north-easterly ditions of Stenness in lat. N. 59o. Such a comparison direction. Measuring the azimuth of the alignment will show how useless it is to pursue these inquiries on Lukis's plan, and finding the horizon elevations without taking the latitude and the height of the from the 1-inch Ordnance map, we have the followsky-line into account.

ing :The Stripple Stones(lat. 50° 32' 50" N.,

N. 28° E.' long. 4° 37' W)

33° 47' N.

Capella 1480 b.c. This is a very remarkable circle consisting of 5 It may be remarked that here we have a date for erect and ii prostrate stones situated on a circular the

of Capella intermediate between those level platform 175 feet in diameter on the boggy obtained for "The Pipers” and the "Stripple south slope of Hawk's Tor on Hawkstor Downs in Stones " respectively. the parish of Blisland. The circle itself is about 148




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In ordinary vessels the freeboard is considerable, TH HE construction of submarines for the Royal and the sides are approximately vertical between the

Navy began about five years ago. On March lightest draught reached on service and the deepest 31, twenty-five vessels of the class had been com- (load) draught; consequently, within these limits of pleted, fifteen were building, and twelve more were draught, horizontal sections of the vessels coincident projected in the Navy Estimates for 1906-7. France with the water-surface-known as planes of flotation at the same date had thirty-nine submarines com- --remain practically constant in form, area, and pleted, and fifty building or projected. Russia had moments of inertia. In cigar-shaped submarines, with thirteen vessels completed and fifteen building. The circular cross-sections, the freeboard is sinall, and the United States had eight vessels completed and four lightest draught of water bears a large proportion to building, while Congress has recently sanctioned a the diameter of the largest circular cross-section. For special vote of 200,000l. for further work on sub- the typical submarine dealt with in the Royal Society marines. Germany, Italy, and Japan as yet have paper, the extreme breadth (diameter of largest crossdone but little, but they are moving in the same section) is a little more than twelve feet, and the lightest direction. An American engineer, Mr. Holland, has draught of water is about ten feet. The circular form exercised the greatest influence on recent submarine of cross-section involves rapid diminution in lengths, design, having worked at the problem for thirty breadths, areas, and moments of inertia of successive years, and proved himself a worthy successor of his planes of flotation as the draught of water is infellow-countrymen Bushnell and Fulton, who were creased from light to load. These changes are acpioneers in submarine construction in the closing years companied by rapid and considerable losses in the of the eighteenth century and the commencement of stability, and the conditions differ radically from those the nineteenth. The first five British submarines, of ordinary ships. For the typical submarine the extreme ordered in 1900, were repetitions of a type designed length is 150 feet, and breadth extreme 12.2 feet; but by Mr. Holland, tried and approved by the United the length of water-line at the lightest draught is only States Navy Department. Great developments have 94 feet, and breadth 8.2 feet. When the draught of taken place in later British submarines. Those first water is increased eighteen inches (by admitting built had displacements of 120 tons, surface speeds water-ballast) and the vessel is prepared for diving, the of eight to nine knots, and gasoline engines of 160 length at the water-line falls to 41 feet, and the horse-power. Vessels now building have displace- breadth to 3.6 feet. In the cruiser of ordinary form ments exceeding 300 tons, a surface speed of thirteen an equal change of draught produces small change knots, and gasoline engines of 850 horse-power. The in length, breadth, and area of the planes of flotation, cost of the earlier vessels was about 35,000l. ; that of and these dimensions are practically equal to the ex. the later vessels must be twice as great. Other treme length and breadth of the vessel. For the countries have taken similar action, and some are cruiser the moments of inertia of successive planes of building still larger vessels.

flotation about their principal axes remain nearly British submarines are kept continuously at work, constant within these limits of variation in draught; and this experience has yielded valuable information whereas for the submarine moments of inertia leading to successive improvements. The vessels diminish rapidly as the draught of water is increased. chiefly used for experimental purposes up to date in the cruiser the extreme length is 260 feet, and the belong to the "A" class-200 tons in displacement metacentre for longitudinal inclinations is 352 feet and ten knots surface speed. Vessels of this class above the centre of buoyancy at light draught, and consequently have been most before the public. Their 328 feet when the draught is increased by eighteen active employment has not been free from accidents, inches. In the submarine the extreme length is but, having regard to novelty of type and special 150 feet, but the corresponding height of longitudinal risks which unavoidably accompany the power of sub- metacentre above centre of buoyancy is only 37 feet mergence, it is a matter for congratulation that these at lightest draught, and falls to 11 feet when the accidents have not been more numerous and serious vessel is prepared for diving. At the lightest draught in their consequences. Official inquiries have been the power of the submarine to resist longitudinal made into the causes of accidents, and reports have inclinations (changes of trim) is relatively small; in been published. In the opinion of the writer these the diving condition it is diminished almost to vanishproceedings showed a tendency to minimise risks ing point. It will be understood, therefore, that necessarily encountered in working submarines. He when a submarine is prepared for diving every man consequently undertook a lengthy series of calcula- has to remain at his station, and no weights must tions for typical submarines of different dimensions, be moved; every opening into the interior must be in order to ascertain their conditions of stability in closed herinetically. The reserve of buoyancy is exvarious conditions which occur on service. The re- tremely small in the diving condition. A submarine of sults for one class are embodied in a paper presented more than 200 tons weight may have only 400 to 800 to the Royal Society on May 3, which paper contains pounds reserve-representing 40 to 80 gallons of water. also the results of similar calculations made for a Even at their lightest draughts the reserve of cruiser of ordinary form. The distinctive conditions buoyancy of submarines is very small as compared of submarines were emphasised by comparing these with that in other vessels. In good examples it is results, and the editor of NATURE has suggested that 6 per cent. of the corresponding displacement-little an explanation in popular language of the principal more than half the lowest percentage accepted for conclusions, based on the investigations, may be of

low-freeboard monitors when fully laden, and about general interest.

one-fourth the corresponding percentage for the Submarines are generally “cigar-shaped,” with deepest laden cargo steamers. Openings into the incircular or nearly circular cross-sections. This form terior are placed at the tops of conning towers at a is adopted in order to provide, with a minimum ex- considerable height above water, and Admiralty penditure of weight, structural strength sufficient to regulations provide that all openings shall be closed meet severe external fluid pressures which may come before water-ballast is admitted to bring a vessel into upon the hulls if submarines sink to considerable the diving condition. Further, it is now provided depths. Such depths are not reached intentionally, that before proceeding at full speed at the surface, the but experience shows that they may be attained acci- maximum reserve of buovancy shall be secured by dentally, and that very quickly.

emptying ballast tanks. One of the most serious acci


dents that have occurred to British submarines--that especially when applied to large vessels, involves LO A &-was unquestionably due in great measure to risks of reaching great depths in a short time before proceeding at full speed with about half the maximum buoyancy can be restored. This is recognised in reserve of buoyancy, certain tanks containing water- vessels which work on that system, and detachable ballast. The vessel was driven under water as she external weights are fitted, so as to restore buoyancy gathered peed, dipped her bow suddenly, brought in cases of emergency. ihe open top of the conning tower to the water- There has been a considerable increase in the speed level, was partly filled, and foundered.

of submarines, both at the surface and when subMaintenance of the full reserve of buoyancy and merged. Our latest types are said to have surface lightest draught of water when proceeding at the speeds of thirteen knots and a radius of action of surlace increases safety in two directions. It secures 500 miles with their gasoline engines, while the undermuch greater longitudinal stability, and diminishes water speed is ninc knots and radius of action 90 the tendency to plunge produced by the relative miles. These higher speeds are attainable, no doubt, motions of the water surrounding the vessel, especially but they necessarily involve greater risks, especially at the bow. These motions are largely discontin in the diving condition. Pressures on horizontal uous, broken water being piled upon the bow, and rudders increase as the squares of the speeds, and the the phenomena being of such a character that only extreme sensitiveness of submarines when submerged direct experiment on models or vessels can give ac- to the action of external forces tending to produce curate information. Such experiments have been changes of trim must demand much greater watchfulmade both in this country and abroad, and they in- ness, skill, and promptness of action on the part of dicate the occurrence of a tendency to plunge at steersmen than are now required, if greater speeds certain critical speeds. The problems are still only are to be attained under water. The risks of attainpartially solved, but it is certain that the maximum ing rapidly excessive depths of submergence must reserve of buoyancy should be maintained. It also increase as speeds are raised, and they are now far appears desirable to keep the vessels on an even keel, from negligible. At the lightest draughts increase since a cigar-shaped form has then its maximum of speed would also involve greater risks of accilongitudinal stability for a given mean-draught of dental plunging. Exhaustive experiments are neceswater. In the Royal Society paper calculations are sary, therefore, before designers of submarines commit recorded showing the diminution of stability accom- themselves to the production of vessels having much panying changes of trim in submarines.

greater surface speeds, and still more of vessels having In modern submarines of large size the operation much greater under-water speeds. Submarine design of diving is performed when the vessels have head- is not a task to be lightly undertaken by amateurs; way. Horizontal rudders, controlled by skilled men, it requires thorough experimental and scientific treatare employed as the active means of depressing the ment by competent naval architects, who should be bow. The pressures on the upper surface of the vessel furnished by naval officers with the strategical and resulting from the relative movement of the sur- tactical conditions to be fulfilled in the completed rounding water develop a vertical component acting vessels, and should ascertain what is involved in the downwards which overcomes the small reserve of fulfilment of these conditions.

W. H. WHITE. buoyancy and the vertical component of the pressures on ihe rudder. The submarine then moves obliquely downwards. When the desired depth below the THE RISE AND PROGRESS OF THE surface has been reached the steersman operates the

ZOOLOGICAL SOCIETY.1 horizontal rudders in such a manner that the vessel shall advance on

T was a happy thought on Mr. Scherren's part a practically horizontal course,


to tell the story of the Zoological Society of although it really is an undulating one. Watchful- | London, and he is to be congratulated on the success ness and skill are necessary to achieve this result, and with which he has accomplished his evidently conthere must be no movements of men or weights | genial task. The history of a development is always which would vary the position of the centre of gravity. interesting, especially when it is still progressing, If such movements become necessary-as, for ex- and there is, moreover, a strong personal interest in ample, when torpedoes are discharged-compensation the book, since many eminent workers, whose names must be arranged to take effect at once. Failures and deeds are familiar, have cooperated in various to comply with these conditions may involve serious ways in furthering the welfare of the society since consequences, and have caused submarines to dive to

its inception in 1826. Mr. Scherren's book is not great depths. With trained and disciplined crews only a careful contribution to the history of zoology such accidents are rare. Plans for automatic main- in Britain during the last eighty years, but is at the tenance of any desired depth-similar to those used

same time good reading for its revelation of what in locomotive torpedoes—have been brought forward goes on behind the scenes in a scientific society, and and tried; but for large submarines manual control

for its record of many interesting events in what is has been found preferable. In small submarines it familiarly called the Zoo." has been found possible to dive without headway On November 29, 1822, John Ray's birthday, a by varving the volume of displacement, admitting bud from the Linnean Society formed itself into a Walps into suitable chambers from which it can be “ Zoological Club,” which four years afterwards took readily expelled when the desired depth has been shape as the Zoological Society. There were 342 spached, and a balance restored between weight and members at the close of the year, and there are now buoyancy. Such methods involve the necessity for ten times as many. In 1828, when the gardens were minute and rapid adjustments, which can be secured opened to the public, there were about 600 specimens, on a small scale much more readily and certainly and there is now a specimen for each F.Z.S. A than in a large scale. Is a consequence, horizontal

farm for breeding purposes and experimental work rudders and headway have been generally adopted for (from which nothing very noteworthv ever resulted) large submarines, and have answered well on the

was established in 1829 at Kingston Hill, and scientific whole. One great advantage of the plan is that when meetings began to be held in 1830. Such were the headway censes the horizontal rudders bucome in

1 "The Zoological Society of London: a Sketch of its Foundation and operative, the small reserve of buoyancy reasserts Development, and the Story of its Farm, Museum, Gardens, Menagerie itself and the submarine comes to the surface. The and Library." By Henry Scherren, F.Z.S Pp. xii +252 ; 12 coloured other systeti-varying the volume of displacement plantes Price coloured plates, 9 plans. (London : Cassell and Co., Lid.,

1905.) . NO. 1910, vol. 74]

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