74- 
first REPORT— 1831. 
stomach daily was..... Ill oz# 
of which there passes off sensibly . 1 
Leaving for the waste by insensible perspiration 10| oz. 
Mr. Dalton had ascertained from experiments on his own 
respiration that the quantity of Carbonic acid gas expelled 
from his lungs contained of Carbon . . lOf oz. 
His daily loss by perspiration of aqueous vapour from the 
lungs was at the same time found to be 20J oz. to which 
adding lOf oz. Carbon, we have the total loss by perspiration 
from the lungs, oOf oz., which taken from 37J, leaves 6f oz. 
per day for the insensible perspiration of the skin, of which 
6| oz. are water, and \ oz. is Carbon. 
The element Azote, of which \\ oz. per day was taken into 
the stomach, appears to have passed off by evacuation. Of 
the 6 lbs. of aliment taken in a day, 1 lb. consists of Azote and 
Carbon, and 5 lbs. of water, and nearly the whole quantity of 
food taken into the stomach enters the circulation,—the residual 
part constituting only T V of the whole,—of which about half is 
thrown off by the kidneys, more or less according to season and 
climate, another part passes off by insensible perspiration, | 
being perspired from the lungs, and ^ from the skin. 
Mr. R. Potter read a paper containing remarks on a the¬ 
ory of the late M. Fresnel concerning the reflection of light 
from the surfaces of bodies. 
M. Fresnel in a paper read before the Academy of Sciences 
in Paris, and of which he published an abstract in the Annales 
de Chimie for 1820, proposed to account for the reflection of 
light at the surfaces of bodies, on the undulatory theory, by 
its impinging on the ponderable particles. He appears to have 
afterwards in some measure modified his views, but not, to 
the writer’s knowledge, ever to have formally renounced his 
former proposition. Hence the subject may fairly be con¬ 
sidered as still open to discussion : and the manner of consider¬ 
ing reflection, as caused by the light striking the ponderable 
parts of bodies, being the one which almost every person would 
recur to, on first commencing the study of physical optics, it will 
perhaps be considered not entirely useless, on this account also, 
to enter into a regular examination of M. Fresnel’s hypothesis. 
Now if reflection were caused immediately by the ponderable 
matter in any surfaces, it ought to be some function of the 
quantity of matter in the bodies furnishing such surfaces ; but 
even a superficial view of the small quantity of light reflected 
