SILK-WORMS. 
77 
The silk worms-proceeding from one ounce of 
eggs, consume — 
den change from moderate heat to violent heat, it cannot hear. 
Rapid changes in general from heat to cold, and cold to heat, 
are highly injurious to it. In its native climate it is not ex- 
posed to these vicissitudes, and therefore thrives well, with- 
out requiring all the care we are obliged to bestow on it. 
With us, on the contrary, the temperature of the atmosphere 
is so variable, that without artificial means, we could not fix 
it in our laboratories, for rearing silk-worms. A series of 
experiments has proved, that in France, 6S° is the most suit- 
able to the silk- worms. Some cultivators have raised it 
as high as 73° and even 77° with good success. We must 
not lose sight of this fact, that it is not heat that affects the 
silk-worm, but sudden transitions from one temperature to 
another. Such as making it pass from 6S° to 77° in one day, 
I am convinced would greatly annoy it, and injure its health. 
If it happen to be necessary to hasten the worms in conse- 
quence of the advanced state of the mulberry leaf, which can- 
not be retarded, it should be done gradually, so that they 
perceive not the alteration. The silk-worm suffers as much 
from difficulty of breathing in bad air, as from sudden changes 
of temperature. M. Boissier de Sauvagues will shew us by 
his experiments, to what degree the heat may be raised in 
rearing silk-worms, without fear of injuring them. “ One 
year, when hurried by the early growth of the mulberry 
leaves, which were developed towards the latter end of April, 
I gave the silk-worms 100° of heat during the two first days 
after hatching, and about 95° during the remainder of the first 
and second age. There elapsed only nine days from the hatch- 
ing, until the second moulting or casting, inclusively. Those 
of the trade who saw the process, could not imagine the 
silk-worms would be able to stand so intensely hot and over- 
coming an atmosphere. The walls and wicker hurdles were 
so heated, they could scarcely be touched. All thought they 
must be burnt, must perish ; however, all went on perfectly 
well, and to their great surprise, I had a most abundant 
