754 Notices respecting New Books. 
selected in which the motion of the earth was in the plane of 
the apparatus. In the first part of July, the direction of 
motion at these two times apparently differed by 115°; the 
morning and evening sets of observations were combined by 
taking into account this difference. In all, more than 250 
turns were observed. 
The velocity of the earth in July may be assumed to be 33°5 
kilometres a second. The length of path in our apparatus 
was 32°2 metres, and the effect to be expected (on the original 
theory) is 1‘4 wave-lengths. 
We have established that, if there is any effect, it is not 
more than 0°015 wave-length. 
LXXVII. Notices respecting New Books. 
The Theory of Heat. By Tuomas Preston, F.RS. Second 
Edition, revised by L. Rogerson Correr, M.A. (Dubl.). 
Macmillan & Co., Ltd. 1904. 
[P is nearly ten years since the late Professor T. Preston wrote his 
‘Theory of Heat.’ The work was written ina marvellously short 
time, taking into account its wealth of carefully compiled abstracts 
from recent sources as well as its fresh and interesting treatment 
of the classical literature of this branch of science. The book, in 
short, had merits which placed it at once among the best textbooks 
on Heat in this or in other languages. There were, however, 
omissions, felt to be such even then; and, of course, these 
omissions have been growing with each important advance of the 
science. 
The second edition of the textbook is now in our hands, and 
before offering any detailed remarks we heartily congratulate 
Mr. Cotter upon his editorial work as a whole. Mr. Cotter has 
added about 100 pages, not one of which is superfluous, to the work; 
as well as many references which will be of value to students, 
both old and young. We proceed to make some very brief 
comments upon the additions. 
In the first chapter we find a much needed exposition of 
Maxwell’s law of the distribution of molecular velocities in gases. 
In this chapter Preston discusses atomic theories ancient and 
modern. It is a pity, for the sake of completeness, that the 
editorial work on this chapter was hardly recent enough to permit 
of a paragraph on the modern evidence in favour of a highly 
complex kineticatom. In chapter II. on Thermometry, Mr. Cotter’s 
additions on the Lag of Thermometers, Pressure Coefficients and 
Errors due to Capillarity or to Emergent Column, are excellent. 
In Pyrometry and Low Temperature Thermometry, a résumé of 
recent methods depending on thermo-electric effects, viscosity of 
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