*70 Notices respecthig New Books, ' 
density of caloric, temperature, cohesion, and attraction of finite 
masses, \vhich result from these investigations, we must refer to the 
memoir itself. 
We shall notice, in the last place, Mr. Holditch’s memoir “ On 
Rolling Curves.” The object of this paper is to determine curves 
of such a form that, revolving about two centres, one of them may 
communicate motion to the other, as in the case of the teeth of 
wheels ; with the condition that the curves, in this communication 
of motion, are to roll upon each other without friction. Euler in 
the Acta PetropoUtana had deduced the characteristic property of 
these curves, but he did not follow out the investigation so as to 
furnish actual forms of curves ; nor has the method of obtaining 
such curves been pointed out by any previous writer. They are 
commonly found by a tentative process ; but Mr. Holditch thought 
it worth while to search for rules and forms for their construction ; 
and these he has found and given the present memoir. Some of the 
results are very curious and novel. 
Pi'inciples of General and Comparative Physiology, intended as an In- 
troduction to the Study of Human Physiology, and as a Guide to 
the Philosophical pursuit of Natural History. By William B. 
Carpenter, M.R.C.S., late President of the Royal Medical and 
Royal Physical Societies of Edinburgh, ^c. 8^c. With 240 Figures 
on Copper and Wood. London, 1839. 8vo, pp. 480. 
The science of physiology has been too generally considered by 
physical philosophers as beyond their pale. The nature of the 
phsenomena which it embraces, and the mode in which it is to be 
pursued, have been regarded as sufficiently distinct to limit the cul- 
tivation of it, with few exceptions, to those who make it a part of 
their regular professional studies. We cannot but think that such 
a state of things may be advantageously modified. Men of general 
science are constantly invoking the aid of the physiologist, for the 
determination of most important and intricate questions ; and too 
often is it found that this aid is unattainable, in consequence of the 
exclusive notions of the latter, who, from his want of truly philoso- 
phical principles, cannot meet the difficulties which he is expected 
to solve ; and, on the other side, physiologists are too often con- 
tent with a smattering of knowledge on physics and chemistry, 
which is more likely to lead them wrong than right. We do not 
mean to assert that there are not many bright exceptions on both 
sides ; but we maintain that the cause of philosophy would be 
benefited if the barrier which is supposed to exist between the sci- 
ence of vitality and that of general physics were broken down, and 
if the cultivators of each were to make themselves acquainted with 
the principles of the other, and with the best mode of pursuing and 
extending both. 
Sucli appears to have been the object of the author of the volume 
before us. I"rom the dedication of it to Sir J. Herschel, we infer 
that lie lias been trained in the school of physical science ; and 
throughout the work we perceive the influence of those grand prin- 
