140 
THE ART OF REARING 
kills them, although an hour before they may have 
looked well, and were nearly ready to rise to the 
boughs. In high regions, where the air is always 
drier and more active, these losses are less fre- 
quent. 
I conclude this paragraph by observing, that 
the hygrometer gives the cultivator timely warn- 
ing, whenever the laboratory is in danger, that 
those easy precautions may be taken which will 
ensure its safety, by removing the peril *. 
2. Concerning the Bottle which Purifies the Air of 
the Laboratory . 
The application of physical science to theoretical 
* The Canon Bellani, of Milan, a philosopher of whom 
M. Dandolo speaks, page 45, has invented a useful instru- 
ment for clever cultivators, which he calls an Eudiometer. 
This term explains its use, as it indicates the exact degree of 
the purity of the oxygen gas contained in atmospherical air. 
By the help of this instrument, it is easy to discover if the 
strata of air immediately above the bed of the silk-worms 
contain sufficient vital air, or if they arc loaded with fixed air, 
or carbonic acid gas. With the Eudiometer at hand, the cul- 
tivator may discover, at any moment, the vitiated state of the 
air in any part of the laboratory. It is not necessary, says 
M. Dandolo, that every cultivator should possess this in- 
strument, but it would always be advantageous to an en- 
lightened one, who should know that the art of rearing silk- 
worms is susceptible, in time, of reaching great perfection, 
which will never be the case without the aid of physical science, 
and the instruments which so greatly promote the success of 
the crops. 
