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. R. N. 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 touchupon. 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., 
vi1., 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 reswmé 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 an 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. 
ALTHOUGH, 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 
