October 29, 19 14] 



NATURE 



227 



he conclusion drawn by me in Nature of October 22, 

 hat Michelson and Morley's repetition of the experi- 

 nent, when correctly interpreted, is in close agree- 

 ment with the predictions of the principle of relativity. 

 This being so, it may be worth while to direct atten- 

 ion to certain facts in connection with that experiment 

 which render it quite inconclusive. 



(i) On the ground of an experimental device for 

 estimating the pressure gradient at different points of 

 he tube, Michelson and Morley assume that the 

 elocity along the axis is equal to 1165 times the mean 

 velocity. This is in sharp contradiction with the 

 theory of the flow of liquid in a tube which shows that 

 the axial velocity is twice the mean. 



(2) The beam of light which traverses the tubes 

 appears from the figures given to occupy a consider- 

 able fraction of the whole area of the tube, and is thus 

 subject to a retardation in phase which varies with 

 the variation of the velocity- of the liquid at different 

 distances from the axes. It may be shown that the 

 retardation in phase of the resultant disturbance when 

 brought to a focus is equal to that which would be 

 produced if the velocity of flow were uniform and 

 equal to the mean velocity over the part of the tube 

 occupied. If this were the whole tube the result of 

 applying these corrections would be to increase the 

 result given by Michelson and Morley for the con- 

 vection coefficient from 0434 to 0-515. On the other 

 hand, if the diameter of the beam were about 0-93 of 

 the diameter of the tube the mean velocity would be 

 so much greater that the convection-coefficient would 

 be reduced to the theoretical value given by the 

 formula of Lorentz, viz., 0-451. There is thus a pos- 

 sibility of general agreement, but the experiment is 

 quite indecisive. 



The announcement that Prof. Zeematj has repeated 



che experiments with great care and with mono- 



I chromatic light and has succeeded in observing a 



dispersive effect is, therefore, of great importance, and 



"is detailed results will be awaited with much interest 



Amsterdam Proceedings, September 26). 



E. CUXXINGHAM. 



St. John's College, Cambridge, October 26. 



Flint Fracture. 



Mr. Lewis Abbott's letter in Nature of October 22 

 is almost entirely irrelevant to the subject of my com- 

 munication to Nature of September 24. In this note 

 I dealt solely with one form of flint fracture, viz., the 

 large, flat, non-conchoidal fractures, surfaces which are 

 produced by a certain type of " cleaving " blow, and 

 ■ ointed out how it is possible to determine the nature 

 nd direction of the fracturing-agent by the recognition 

 of the fissures of varying size radiating from the point 

 of impact. Mr. Abbott, however, states, these "are 

 certainly not fissures " ; but an examination of these 

 markings upon a flint and a reference to the meaning 

 -f the word "fissure" in a dictionary will convince 

 nyone that my description is correct. 

 The major part of Mr. Abbott's letter deals with 

 -ubjects upon which my former note has no bearing, 

 nd though I agree that these are important 

 nd need investigation, yet it seems regrettable, if the 

 roblems they present were, as Mr. Abbott infers, in 

 recess of solution several years ago, that the know- 

 ■dge already acquired at that time has not up to the 

 resent been laid before the scientific world. It is to 

 e hoped that Mr. Abbott may be able to induce the 

 •Hector who interviewed the late Sir John Evans 

 ' do so without delay. J. Reid Moir. 



12 St. Edmund's Road, Ipswich, October 23. 



NO. 2348, VOL. 94] 



TOWARDS NATURE-STUDY.^ 

 (i)p ROF. ABBOTT'S aim is to give " a simple 

 ■*- statement of the fundamentals of General 

 Biology," both for the general reader and the 

 laboratory student. He deals with both plants 

 and animals, shifting his field so as to get the 

 best illustrations. The main subjects discussed 

 are — living substance, the primary- functions, 

 metabolism, growth, differentiation, development, 

 variation and heredity, organic resj>onse, species 

 and their origin. The book is well-illustrated and 

 marked by three other qualities — an admirable 

 clearness which points to teaching experience, a 

 pleasant freshness of treatment which is in part 

 due to the numerous references to recent work, 

 and an all-roundness of survey, for almost even.- 

 aspect of biology is at any rate recognised and 

 illustrated. This third quality lays the book open 

 to the disadvantage of sometimes saying too little, 

 but most introductory books of this sort say far 

 too much. But we should have liked, for in- 

 stance, to know more about those sea birds which 

 "lay their eggs on the bare rocks and pay no 

 more attention to them thereafter." 



(2) Prof. J. R. Ainsworth-Davis is a firm be- 

 liever in the value of " nature-study " as a factor 

 in increasing efficiency, and his book — an outcome 

 of large experience — is meant to indicate how the 

 subject may be best dealt with, especially in 

 countr}' schools. After clearly indicating how 

 arithmetic, for instance, may be made vital in 

 the country schools by being applied to actual 

 problems, he proceeds to show this is even more 

 essential in connection with nature-study. For 

 this reason the book gives prominence to common 

 plants and animals and familiar physical pheno- 

 mena. In regard to the part dealing with plants 

 and animals, however, it apjjears to us that the 

 author falls far short of his counsel, telling too 

 much and suggesting too little. It is good 

 pemmican, but it is pemmican. In his introduc- 

 tion he protests against the "informational 

 obsession," and upholds "the educational ideal"; 



1 (i) " The Elementary Principles of General Biolopy." By Prof. J. F. 

 A^-bott. Pp. xvi+32<j. (New York: The Macmillan Co. Loodoo : 

 Macmillan and Co., Ltd.. 1914.) Price (s. fyi. 



(2) " The Pursuit of Natural Knowledge." By Prof. J. R. Ainsworth- 

 Davi«. Pp. iv.+234. (Cheltenham: Norman, Sawyer and Co., LtH., 

 1914.) Pnce IS. net. 



(3) " Animal Life by the Sea-shore. By Drs. G. A. and C. L. Bouleneer. 

 Pp. xii+83+plates. (London : Offices of Country Life, Ltd., n.d.) Price 

 5f. net. 



(4) " T\i- Naturalist at the Seashore." By R. Elmhirst. Pp. viii+86+ 

 8 plates. (London : A. and C. Black, 1913.) Price is ixL net. 



(5) " Bird Studies in Twenty-foar Lessons." By W P. Westell. Pp. xii 

 -{-15a. (Cambridge: LTni»ersity Press, 1914.) Price ■2s. f>d. net. 



(6) "Common Briti!^h Beetles." By Rer. C A. Hall. Pp. Tii+86. 

 (London : A. and C. Black, 1914-) Price \s. bd. ret. 



(7) "Odd Hours wiih Nature." By Alexander Urquhart. Pp. 323+ 

 plates. (London : T. Fisher Unwin. n.d.) Price 5J. net. 



(8) Ernst Haeckel : " Die Natur als Kun.<;tlerin." Nebst : Dr. W. 

 Breitenbach ; " Formenschatz der Schoi>fiing." Pp. 114- (Berlin: Ch. Vita, 

 Dfutsrhes Verlaghans, n.d.) 



(9) "A Natural History of l<oamemoath and District," including 

 Archaeolofiy, Topography, Municipal < -OTemment, Climaie, Educatioo, 

 Fauna, Flora and Geology. By the Members of the Boumemoath Natural 

 Science Society. Edited by Sir Daniel Morris. Pp. xiv — 400. (Boume- 

 moutb : Natural Science Society, 1914.) Price is. (id. net. 



(10) " Handbuch der ns>turgeschichilichen Technik fur Lehrer und 

 Studierend* der Naturwissen^chaften." Hrransgegeben von Prof. Bastian 

 .SchraiH. Pp. viii-f-555. (Leipzig and Berlin: B. G. Teubner, 1914.) 

 Price 15 marks. 



(11) " Biologen-Kalender." Edited by Prof. B. Schmid und Dr. C 

 Thesing. tn-ter Jahrgang. Pp. ix+513. (Leipzig and Berlin : B. G. 

 Teubner, 1914)- Price 7 marks. 



