544, Intelligence and Miscellaneous Articles. 
arises whether hailstones are not formed under similar circumstances. 
In a memoir which I shall publish in the Bibliotheque Universelle, 1 
examine this analogy more closely, and endeavour to show that it is 
not superficial, but extends into numerous details. I attempt to show 
that this particular case of freezing gives a suitable explanation of 
the general phenomena, as well as of the accidental peculiarities of 
hailstones: I attempt to show that these aqueous globules may also 
be cooled below 0° in the atmosphere; that they can then freeze and 
unite just as in the mixture of chloroform and oil, and that the grains 
of ice thus formed, increased by the condensation of atmospheric 
vapour on their surface, may be hailstones.—Comptes Rendus, 
April 15, 1861. 
ON AN APPARATUS FOR EXPERIMENTS ON RESPIRATION AND 
PERSPIRATION IN THE PHYSIOLOGICAL INSTITUTE AT MUNICH, 
BY PROFESSOR PETTENKOFER. 
In order to determine the quantities of carbonic acid and of water 
which are eliminated through the skin and lungs, numerous methods 
have been proposed, and the processes and results of Scharling, 
Vierordt, Valentin and Brunner, Regnault and Reiset, Smith, and 
others, are well known to every physiologist and chemist. The 
objections to all previous methods are of two kinds: first, that the 
accuracy of the method cannot be determined by control experiments 
with known quantities of carbonic acid; and second, that the men 
and animals were compelled to breathe, in these experiments, under 
more or less unusual and burdensome, and therefore unnatural con- 
ditions. ‘The experiments of Bischoff and Voit on the food of car- 
nivora have further shown that the carbonic acid eliminated by the 
lungs and skin, cannot be obtained by taking the difference between 
that administered as food, and that secreted in the urine and feces, 
allowing for the difference in weight of the body; because two un- 
known quantities of carbonic acid and water are eliminated from the 
lungs simultaneously, and in varying quantities. As it was neces- 
sary to determine directly at least one of these magnitudes, the 
author endeavoured to construct an apparatus by which a constant 
current of air could be passed over a man, and the increase of car- 
bonic acid and water of this air determined. 
Pettenkofer’s apparatus consists of a small sheet-iron chamber 
(which will be called the saloon) 8 Bavarian feet in every dimension, 
with an iron door, a light at the top, and windows at the sides. 
The windows were cemented, and the sides and cover riveted 
as air-tight as possible. The door had moveable openings in order 
to ensure access of air at other points besides the joints of the door. 
On the side opposite to the door there are two apertures, one 
below and the other above, which, by means of two tubings, are con- 
nected with a single wide tube outside, in which the air flows towards 
that part of the apparatus which serves as an aspirator. ‘l'his piece 
of the apparatus, which is placed in a different part of the house, con- 
sists of two suction cylinders with valves, which can be uniformly 
worked to the same height of stroke by means of a powerful clock- 
work motion, The weight of the clockwork is continually raised in 
