August 27, 1885] 
NAROECE 399 
that matter during one second is equal to its radiation 
during the same time, and this holds for all kinds of heat. 
On the other hand, if we take a single molecule and a 
billionth of a second, we cannot affirm the same equality. 
This is no doubt correct ; in fact, if the equality between 
radiation and absorption were to hold for the smallest 
conceivable mass and the smallest conceivable increment 
of time, our equilibrium would in reality be a tensional 
one instead of being movable or dynamical. I shall con- 
clude by repeating the words of Tait (“ Heat,” p. 253) :— 
“Tt is vain, at least in the present state of science, to 
look for a truly 7Zgorous investigation of the relation 
between radiating, absorbing, and reflecting powers. In 
all the professedly rigorous investigations which have 
been given the careful reader will detect one or more 
steps which are to be justified only by the statistical pro- 
cess of averages.” BALFOUR STEWART 
(To be continued.) 
THE LIFE OF AQUATIC ANIMALS AT HIGH 
PRESSOR E 
HE magnificent expeditions of the 7a//sman and the 
Travatlleur have called the attention of naturalists 
and physicists to the conditions of life at the bottom of 
the sea. A learned physiologist, Dr. Regnard, has con- 
ceived the happy idea of studying experimentally these 
condition of life at high pressure. With apparatus de- 
signed by M. Cailletet, he has subjected aquatic animals 
to enormous pressure, such as prevails in the depths of 
the ocean, and has examined the results when those in- 
habiting the surface are suddenly placed at great depths. 
Since his first experiments Dr. Regnard has invented an 
ingenious method by which he can see, notwithstanding 
the great pressur2, what goes on inside the apparatus. 
Fic. 1.—General View of Dr. Regnard’s Apparatus. 
Hitherto the operator simply placed the animals on 
which he experimented in the iron block of the Cailletet 
pump, and subjected them to the pressure corresponding 
to a given depth ; he then released them, sometimes very 
slowly (after several days), sometimes rapidly and even 
instantly. He examined then, physiologically and micro- 
scopically, the lesions produced. But all the intermediate 
stages between the entrance of the animals and the time 
they were taken out escaped the observer. But now the 
apparatus in Fig. 1 allows him to follow each minute the 
effects. The following is Dr. Regnard’s description of his 
apparatus to the Academy of Sciences :— 
Two holes are pierced through and through across the 
lower part of the Cailletet block, M (Fig. 2). In these 
two holes, placed in a straight line, are inserted two tubes 
inv andr’, These are hollow, and in each of them is 
* From La Nature 
solidly fixed a cone of quartz, B, the extremity of which 
joins the edges of the hole which is pierced in the screw 
nut E. A ray of light thrown by the orifice ~ will thus 
traverse the apparatus and emerge at 7’. Experiments 
have shown that a similar apparatus will resist easily a 
pressure of 650 atmospheres, which represents that of the 
greatest depths that have been dredged—about 6500 
metres. Across one of the quartz cones are sent the con- 
centrated rays of an electric lamp. These rays cross the 
| block full of water, and emerge on the opposite side, 
where they are received by an achromatic object-glass 
which projects them on to ascreen. The observer there- 
fore works at a distance from the apparatus, where he is 
sheltered from all danger (Fig. 1). This arrangement has 
another advantage. The orifice pierced at 7 is hardly 
half a centimetre in diameter, and one can experiment 
with animalculaz so small as to be scarcely perceptible 
