Miscellanies. 371 
posed, a red hot ball may pass at a little distance before it, without 
causing the least movement in the needle. It was difficult, after 
having observed the immediate permeability of alcohol, oil and nitric 
acid, to believe that the non-permeability of water depended on its 
liquidity. Experiments, however, made with water in the solid 
state, have not varied the result. This property of water seems, 
therefore, to depend on its chemical composition and not on its phys- 
ical condition. 
The third series of experiments was made to determine the spe- 
cific heat of insects, of phosphorus, and of the lunar rays. 
With respect to insects, it has long been thought that their tem- 
perature was that of the circumambient air. It is certain, however, 
that these animals respire, that carbonic acid is formed by them, and 
consequently that a slow combustion must be going on which ought 
to produce some elevation of temperature. Davy was of opinion 
that their temperature was superior to that of the atmosphere. In 
fact, by introducing a very small thermometer into the bodies of in- 
sects, a slight elevation of the mercury generally occurred. In two 
cases, however, there was a depression. But the method employed 
by Davy was very imperfect, Ist, because it is applicable only to 
very large insects; 2d, because the mass of the thermometer being 
very large in proportion .to that of the animal, the instrument would 
produce, by contact, a great subtraction of caloric; 3d, because the 
evaporation of the humors, leaking through the incision, would cause 
a reduction of temperature; and 4th, because the experiments must 
always be made upon an animal in a suffering state. 
With the thermo-multiplicateur these inconveniences may be avoid- 
ed. ‘The experimenters were able, by the arrangement which they | 
adopted, to test the temperature of the ee in a state of perfect 
ease and freedom from constraint, that in every 
case, the instrument indicated a sil increase. 
On comparing the results obtained with lepidopterous insects in 
their different states, MM. Nobili and Belloni arrived at a constant 
law, viz. that caterpillars always have a higher temperature than the 
butterflies and chrysalids which proceed from them. Now, as the 
respiratory apparatus of the caterpillar is more fully developed, and 
respiration more active, than in the perfect insect, it results that the 
theory which attributes animal heat to a slow combustion, is support- 
ed by the phenomena of insect life, as well as by those of the ver- 
tebral animals. 
