June 7, 1906] 



NA TURE 



129 



dents that have occurred to British submarines — that 

 to A 8 — was unquestionably due in },'reat measure to 

 proceeding- at tull speed with about half the maximum 

 reserve of buoyancy, certain tanlis containing^ water- 

 ballast. The vessel was driven under water as she 

 slathered speed, dipped her bow suddenly, brought 

 I he open top of the conning tower to the water- 

 level, was partly filled, and foundend. 



M.iintenance of the full reserve of buoyancy and 

 lii;htest draught of water when proceeding at the 

 >urface increases safety in two directions. It secures 

 much greater longitudinal stability, and diminishes 

 the tendency to plunge produced by the relative 

 motions of the water surrounding the vessel, especially 

 ,il the bow. These motions arc largely discontin- 

 uous, broken water being piled upon the bow, and 

 the phenomena being of such a character th;it only 

 direct experiment on models or vessels can give ac- 

 curate information. .Such experiments have been 

 made both in this country and abroad, and they in- 

 dicate the occurrence of a tendency to plunge at 

 certain critical speeds. The problems are still only 

 partially solved, but it is certain that the maximum 

 reserve of buoyancy should be maintained. It also 

 appears desirable to keep the vessels on an even keel, 

 since a cigar-shaped form has then its maximum 

 longitudinal stability for a given mean-draught of 

 water. In the Royal Society paper calculations are 

 recorded showing the diminution of stability accom- 

 panying changes of trim in submarines. 



In modem submarines of large size the operation 

 of diving is performed when the vessels have head- 

 w;iv. Horizontal rudders, controlled by skilled men, 

 .ire employed as the active means of depressing the 

 bow. The pressures on the upper surface of the vessel 

 resulting from the relative movement of the sur- 

 rounding water develop a vertical component acting 

 dowMiwards which overcomes the small reserve of 

 buoyancy and the vertical component of the pressures 

 on the rudder. The submarine then moves obliquely 

 downwards. When the desired depth below the 

 -.urface has been reached the steersman operates the 

 horizontal rudders in such a manner that the vessel 

 -,hall advance on a practically horizontal course, 

 .ilthough it really is an undulating one. Watchful- 

 ness and skill are necessary to achieve this result, and 

 there must be no movements of men or weights 

 which would vary the position of the centre of gravity. 

 If such movements become necessary — as, for cx- 

 .imple, when torpedoes are discharged — compensation 

 must be arranged to take effect at once. Failures 

 to comply with these conditions may involve serious 

 consequences, and have caused submarines to dive to 

 great depths. With trained and disciplined crews 

 such accidents are rare. Plans for automatic main- 

 tenance of any desired depth — similar to those used 

 in locomotive torpedoes — have been brought forward 

 .Hid tried; but for large submarines manual control 

 has been found preferable. In small submarines it 

 has been found possible to dive without headway 

 by varying the volume of displacement, admitting 

 water into suitable chambers from which it can be 

 readily expelled when the desired depth has been 

 reached, and a balance restored between weight and 

 buoyancy. Such methods involve the necessity for 

 minute and rapid adjustments, which can be secured 

 on a small scale much more readily and certainly 

 than on a large scale. As a consequence, horizontal 

 rudders and headway have been generally adopted for 

 large . submarines, and have answered well on the 

 whole. One great advantage of the plan is that when 

 headway ceases the horizontal rudders become in- 

 operative, fhe small reserve of buoyancy reasserts 

 itself, and the submarine comes to the surface. The 

 other system — varying the volume of displacement — 



NO. 1910, VOL, 74] 



especially when applied to large vessels, involves 

 risks of reaching great depths in a short time before 

 buoyancy can be restored. This is recognised in 

 vessels which work on that system, and detachable 

 external weights are fitted, so as to restore buoyancy 

 in cases of emergency. 



There has been a considerable increase in the speed 

 ol submarines, both at the surface and when sub- 

 merged. Our latest types are said to have surface 

 speeds of thirteen knots and a radius of action of 

 500 miles with their gasoline engines, while the under- 

 water speed is nine knots and radius of action 90 

 miles. These higher speeds are attainable, no doubt, 

 but they necessarily involve greater risks, especially 

 in the diving condition. Pressures on horizontal 

 rudders increase as the squares of the speeds, and the 

 extreme sensitiveness of submarines when submerged 

 to the action of external forces tending to produce 

 changes of trim must demand much greater watchful- 

 ness, skill, and promptness of action on the part of 

 steersmen than are now required, if greater speeds 

 are to be attained under water. The risks of attain- 

 ing rapidly excessive depths of submergence must 

 increase as speeds are raised, and they are now far 

 from negligible. .'\t the lightest draughts increase 

 of speed would also involve greater risks of acci- 

 dental plunging. Exhaustive experiments are neces- 

 sary, therefore, before designers of submarines commit 

 themselves to the production of vessels having much 

 greater surface speeds, and still more of vessels having 

 much greater under-water speeds. Submarine design 

 is not a task to be lightly undertaken by amateurs; 

 it requires thorough experimental and scientific treat- 

 ment by competent naval architects, who should be 

 furnished by naval officers with the strategical and 

 tactical conditions to be fulfilled in the completed 

 vessels, and should ascertain what is involved in the 

 fulfilment of these conditions. W. H. White. 



THE RISE AND PROGRESS OF THE 

 ZOOLOGICAL SOCIETY.' 



IT was a happy thought on Mr. Scherren's part 

 to tell the story of the Zoological Society of 

 London, and he is to be congratulated on the success 

 with w-hich he has accomplished his evidently con- 

 genial task. The history of a development is always 

 interesting, especially when it is still progressing, 

 and there is, moreover, a strong personal interest in 

 the book, since many eminent workers, whose names 

 and deeds are familiar, have cooperated in various 

 ways in furthering the welfare of the society since 

 its inception in 1826. Mr. Scherren's book is not 

 only a careful contribution to the history of zoology 

 in Britain during the last eighty years, but is at the 

 same time good reading for its revelation of what 

 goes on behind the scenes in a scientific society, and 

 for its record of many interesting events in what is 

 familiarly called the "Zoo." 



On November 29, 1822, John Ray's birthday, a 

 bud from the Linnean Society formed itself into a 

 " Zoological Club," which four years afterwards took 

 shape as the Zoological Society. There were 342 

 members at the close of the year, and there are now 

 ten times as manv. In 182S, when the gardens were 

 opened to the public, there were about 600 specimens, 

 and there is now a specimen for each F.Z.S. .\ 

 farm for breeding purposes and experimental work 

 (from which nothing very noteworthy ever resulted) 

 was established in 1829 atKingston Hill, and scientific 

 meetings began to be held in 1S30. Such were the 



1 " The Zoological Society of London : a Sketch of it^ Foundation and 



Development, and the Story of its Farm. Museum. Gardens, Menagerie 



and Library." By Henry Scherren, F.Z.S Pp. xii + 252; i-z coloured 



j plates, 50 uncoloured plates, 9 plans. (London: Cassell and Co, Ltd.. 



1906.) Price 30^. net. 



