300 
Analyses of Books. 
fMay, 
surface of the head, but that the contraction of different muscles 
afleCt the temperatures of different well-defined areas of the 
integument of the head, each muscle having a special thermic 
centre in the cortical substance of the brain, the temperature of 
which centre is increased when the muscle aCts in a degree suffi- 
cient to produce a change of temperature in a circumscribed 
area of the overlying integument, appreciable by means of in- 
struments of no great delicacy. Dr. Lombard and Dr. Haynes 
find, on the contrary, a rise of temperature in fewer than 4 per 
cent of their experiments, whilst the cases in which a fall took 
place were more than five times as numerous. It would seem, 
however, that in many cases muscular movements disturb the 
temperature of the head, causing either elevation, depression, or 
irregular fluctuation. 
In a third course of researches Dr. Lombard examines the 
influence of the temperature of the air upon the temperature of 
the head. He finds that as the average atmospheric temperature 
declines, that of the head falls also, though in a very much 
smaller proportion, a decrease of 11*9° C. in the temperature of 
the air being accompanied by a fall only of i # 6° C. in the tem- 
perature of the head. 
The Collected Works of fames MacCullagh, LL.D., Fellow of 
Trinity College , and Professor of Natural Philosophy in the 
University of Dublin. Edited by J. H. Jellett, B.D., and 
Samuel Haughton, M.D. Dublin : Hodges, Figgis, and 
Co. London : Longmans and Co. 
The memoirs contained in the present volume are chiefly re- 
printed from the “ Proceedings and Transactions of the Royal 
Irish Academy.” The subjects dealt with are Geometry and 
Physical Optics, treated from a mathematical point of view. 
Among the principal of these papers are “ The Double Refrac- 
tion of Light in a Crystallised Medium according to the Principles 
of Fresnel,” “ The Intensity of Light when the Vibrations are 
Elliptica,l,” “ Conical RefraCtion,” “ Recent Investigations con- 
cerning the Laws of Reflection and RefraCtion at the Surface of 
Crystals,” “ Laws of Reflexion from Metals,” “ Laws of the 
Double RefraCtion of Quartz,” “ Laws of Reflexion from Crys- 
tallised Surfaces,” “ Probable Nature of the Light transmitted 
by the Diamond and by Gold-leaf,” &c. These memoirs are all 
perfectly well known to those engaged in the study of Optics, 
so that any examination of their merits would seem an imper- 
tinence. 
As an Appendix we find two papers on Ancient Egyptian 
