136 NATURAL SCIENCE [August 



means of investigation in their own special field of work. Foremost 

 among these are the biologists, and their appreciation of the discovery 

 is evidenced by the recent publication of the beautiful series of 

 radiograms of the British Echinoderms by Prof. E. 1ST. Wolfenden, 

 the British Batrachians and Reptiles by Messrs J. Green and J. 

 H. Gardiner, and many others. We feel sure that the peculiar power 

 of this means of research need only be more fully known to become 

 very largely used. 



Returning to the work before us, there are one or two details that 

 we must touch upon. The " Historical Review " is both interesting and 

 comprehensive, but we scarcely think Prof. Roentgen has been given the 

 prominent place due to him ; he has certainly done more than to apply 

 to practical uses a series of investigations begun by others ; in fact, 

 application to practical uses is just what Prof. Roentgen has not 

 touched upon. We also note the term, ' Crooke's tube ' ; this is 

 possibly a misprint, but should be Crookes' tube. Also, mention 

 is made of a Rhumkorff (? Ruhmkorff) or Apps' coil ; we fail to see 

 the distinction. In chapter ii. (Apparatus), a quantity of very 

 elementary matter is introduced, of which we doubt the utility, 

 for it is not possible, in the space that can be devoted to it, to 

 teach the elements of electricity ; the same must be said of the early 

 part of chapter iv. on photography. 



The various forms of tubes which have been used for the genera- 

 tion of Roentgen rays are very fully illustrated, and are of considerable 

 interest, as also is the description of the new Tesla oscillator and the 

 more recent form of Ruhmkorff coil introduced by Messrs Rochefort 

 and Wydts ; in these particulars the book is thoroughly up to date. 

 The illustrations, particularly the half-tone radiograms, are very 

 good ; but it is almost a pity that these latter are scattered about 

 the book without any particular reference to the text. Chapters v., 

 vi., and vii., on medical radiography, show the advance that has been 

 made in this direction within the last two years. The book concludes 

 with a concise and well-written resume of the various theories that 

 have been advanced as to the nature of the rays. On the whole, we 

 can congratulate the authors upon the masterly way in which they 

 have dealt with the subject, and wish the book a wide circulation. 



" Science is Measurement " 



Notes on Observations, being au Outline of the Methods used for determining the 

 Meaning and Value of Quantitative Observations and Experiments in Physics and 

 Chemistry, and for reducing the Results obtained. By Sydney Lupton, M.A. 

 8vo, pp. x + 126. London : Macmillan & Co. 1898. Price, 3s. 6d. 



Althouch, as indicated in the sub-title, this little book is distinctly 

 intended for the physicist and chemist, still, if we mistake not, it will 

 be of considerable value to the biologist, and, indeed, to students of 

 other branches of natural science. Although there are biologists 

 among us who make much use of mathematical methods in their re- 

 searches, and although there are mathematicians who love to trespass 

 on the domain of the biologist, yet mathematics are, as a rule, some- 

 what of a bugbear to the ordinary student of biology, who, it is prob- 

 able, spent the time he should have devoted to them in running after 

 butterflies or exploring the inside of a frog. For the ordinary biologist 



