136 
THE ART OF REARING 
mometer; but if these instruments should be 
thought too expensive even to effect so impor- 
tant an object as the regulation of the air for silk- 
worms, a plate of kitchen salt, coarsely pounded, 
may answer in some degree. 
When the hygrometer indicates a very damp 
state of the atmosphere, or when the salt appears 
very damp, wood-shavings should be burnt, or 
straw '(Chap. VI.), in the fire-places, to absorb 
the humidity, and replace it by the external air, 
it is lower near the wicker hurdles which are next the pave- 
ment or floor, than it is on those above. 
2d. That the temperature is less exposed to alteration in 
the higher than in the lower parts, which is the reason that 
the worms generally thrive better on the higher, than on the 
lower trays. 
3d. That the dampness predominates in the lower parts of 
the laboratory. 
4th. That the air is renewed with more difficulty in the 
angles of the laboratory, when there arc no fire-places, than 
in any other part. 
5th. That the silk-worms and the cocoons constantly suc- 
ceed best in those parts of the laboratory, where there is a 
continual, well-regulated, and slow current of air. 
6th. Finally, that without the instruments recommended, 
it would entirely depend on those who attend the laboratory, 
as I said in a former note, to conceal from the master the 
degree of temperature, either too high or too low, to which, 
they may, through negligence, have exposed the laboratory. 
All these advantages appear to me most valuable, and give 
a character of precision and regularity to the art of rearing 
silk-worms which had not before been known. There are 
many other arts founded on more simple rules, independent 
of accidental causes, which do not, however, offer so steady 
a degree of precision. 
