NA TURE 



[November 2, 1905 



essential to teach a student that acceleration is the 

 inevitable property of every force. The motion in 

 Atwood's machine is calculated first by the strictly 

 valid method of introducing the tension, and then 

 by the old method of "mass moved = W, + W 2 ; 

 accelerating force =W, — \V„, &c," which latter should 

 either be unmentioned, or, if mentioned, justified (if 

 possible). The formal statement " when a force acts 

 upon a body and causes motion, it is said to do 

 work " (p. 48) is very dangerous doctrine. The 

 tension of an inextensible pendulum cord certainly 

 does no work, though it exists in the motion. Are 

 we to suppose that safety is contained in the word 

 " causes "? If so, the metaphysician must be heard. 

 On the important and almost universal fallacy con- 

 cerning "centrifugal force" the author is a clear 

 and safe guide. 



A large collection of the ordinary statical problems 

 is followed by a discussion of centres of gravity, 

 moments of inertia and rotatory motions of rigid 

 bodies, and a chapter on graphic statics, the whole 

 being illustrated by a large collection of very well 

 chosen examples. M. 



INDUCED RADIO-ACTIVITY. 

 Radium and Ollnr Radio-active Substances; their 



Application especially to Medicine. By Dr. Charles 



Baskerville. Pp. 164. (Philadelphia : Williams. 



Brown, and Earle, n.d.) 

 DROF. BASKERVILLE'S book is disappointing. 

 A On opening a work on a scientific subject by 

 an original worker in the field of which it treats one 

 expects to find the original materials thoroughh 

 digested and worked up, and tin- relative merits of 

 rival theories and conflicting experimental data care- 

 fully weighed; one hopes, too, to find novel sugges- 

 tions for the interpretation of existing data, and 

 hints to guide experimental research in the future. 



In the present work these things are not to be 

 found. It may lie said, broadly, that the book is no 

 more than a collection of abstracts of original papers, 

 put together, indeed, in some approach to a con- 

 si', utive order, as regards subject-matter, but without 

 the attempt to weld them into a homogeneous whole. 

 We constantly find, for instance, that views which 

 have no serious claims to attention, either from the 

 authority of their authors or from the arguments 

 the\ put forward, are treated with quite as much 

 respect as the opposite conclusions of leading 

 workers in the subject, which are supported by strong 

 experimental evidence. 



In some eases the author even goes so far as appar- 

 ently to endorse conclusions which are opposed to 

 his own. On p. 88 we have a picture, underneath 

 which thi' following explanation is given : — 



"This is a radiograph of a gold fish which had 

 hern placed in water rendered radio-active by having 

 :uspi tided in it for 24 hours a closed lube (our italics) 

 containing ten milligrams of radium of high activity. 

 Bj this process the water was rendered radio-active, 

 and the lish was then placed in the water, and, 

 although the radium had been entirely removed, the 



NO. 1879, VOL. 73] 



lish itself was rendered radio-active, and, when placed 

 on a photographic plate, photographed itself by its 

 own radio-activity." 



As Prof. Baskerville, contrary to his usual custom, 

 mentions no name in connection with this experi- 

 ment, we assume that it is his own. None the less, 

 we read, on pp. 92-93 : — 



" Pilfard calls attention to the fact that no authori- 

 tative statement has been given as to the rendering 

 ol water or other substances radio-active by the 

 presence of a closed tube of radium. He further 

 detected defects in tubes, air bubbles, &c, and regards 

 tin' statements concerning induced activity bv means 

 of closed tubes as based upon the use of defective 

 tubes. As Curie and Rutherford have shown, in- 

 duced activity requires a naked exposure to radio- 

 active bodies." 



For our own part, we have no belief in radio-activity 

 having been produced in the fish under the conditions 

 described. The photographic effects may have been 

 due t" imperfect closing of the tube of radium, or they 

 may have been produced by some direct chemical effect 

 of the fish's skin on the film. But however that may 

 be, ihr author's attitude in emphasising equally two 

 opposite statements is not intelligible. Prof. Basker- 

 ville has shown great industry in bringing together 

 the results of different experimenters, but we cannot 

 think that he has presented his collection judiciously. 



GARDEN CITIES. 

 Garden Cities in Theory and Practice. By A. R. 

 Sennelt. \ ol. i., pp. xix + 557. Vol. ii., pp. xii + 

 558. (London : Bemrose and Sons, Ltd., 1904.) 

 Price 2 is. net. 



THESE two handsome volumes represent the 

 amplification of a paper on "The Possibilities 

 ol Applied Science in a Garden City " which was 

 read by Mr. A. R. Sennett before Section F of the 

 British Association in 1903. 



The author first deals very fully with the engineer- 

 ing problem involved in the laying out of garden 

 cities. A comparison of the various plans on which 

 the great cities of the world have been built is given 

 in a most lucid and interesting manner, after which 

 tin- author shows with many clear and convincing 

 arguments that the best type is that known as the 

 rectilinear configuration, which is the one he adopts 



iln worst of all being the curvilinear type, not only 

 from an aesthetic, but also from a practical point of 

 view. 



An interesting account of the rebuilding of London 

 after the great fire is given in chapter ii. The 

 various plans, especially those of Sir Christopher 

 Wren and Sir John Evelyn, are fully discussed. The 

 plan of the former was more or less adopted, although 

 all his proposals were unfortunately not adhered to, 

 with the result that many fine architectural effects 

 are lost to the metropolis. We cannot do better than 

 recommend those who are interested in this important 

 subject to read the author's own account, which 

 should excite interest even in the apathetic. In 

 regard to the spacing out of the area for his proposed 

 garden city, the author has carefully considered ever} 



