SILK-WORMS. 
59 
It requires more wood to heat a room during 
one day, even with the best-constructed fire-places 
and chimneys, than to heat the same room for 
ten days by means of a stove. The principal ad- 
vantage of the small fire-places is not so much its 
warming the air, as its making a draft or current 
through it, as we shall shew hereafter. (Chap. 
VI. and VII.) 
The temperature of this laboratory should be 
carried to 75° ; about 2° lower than the stove- 
room heat which hatched the eggs. 
Experience teaches us, that as the silk-worm 
grows older, and gets stronger, it requires less 
heat. 
Such is the temperature that suits these in- 
sects shortly after they are hatched. Should the 
season be peculiarly unfavourable, and the ve- 
getation of the mulberry-tree checked, it might 
be necessary to slacken the temperature, and thus 
gain a few days by gradually lowering the heat 
to seventy-one degrees, and even to sixty-eight 
degrees, but not beyond that *. 
* A prudent proprietor has done all in his power, when, 
on observing- the season favourable, and the bud of the mul- 
berry shoots in a proper degree of forwardness, he has put 
the eggs into the stove-room. Should the weather suddenly 
change, as it did in 1814, it is then of great use, to have 
the power of backening the hatching of the eggs without 
injuring the worm, as I have before stated, and to prolong 
