78 
THE ART OF REARING 
1st. In the first age, (that is to say, when all 
are hatched, removed, and distributed upon the 
crop. I afterwards tried giving 1 the silk-worms, in their 
first age, from 93° to 95°, 89° to 91° in the second age ; and 
it is remarkable, that the duration of these two ages was 
nearly similar to that of the preceding 1 experiment, in which 
they had experienced some degrees more of heat. Perhaps 
there may he a degree of heat beyond which we cannot affect 
the progress of the silk-worm, ft is to be added, they had 
an equal proportion of food in both experiments to that 
which is given in the common manner of rearing silk-worms. 
It is singular, that these worms, thus hastened in their two 
first stages, consume only five days in moulting the third 
and fourth time, although with only a temperature of S2° : 
whilst those worms that have not been hastened, take seven 
or eight days for each of the two last moultings, in an ex- 
actly similar degree of temperature. It appears sufficient to 
have given the constitution of the insect an impetus to regu- 
late the quick succession of its changes. 
“ This impetus, which we have been describing as operating 
such rapid growth, also gives the insect vigour and activity, 
which they preserve through their after ages, and prevents 
diseases; thus the hastened, or forced cultivation, presents a 
double advantage. It also shortens the care and attendance 
necessary for silk-worms, and sooner ends the anxiety of the 
cultivator, who must necessarily feel anxiety until the cocoon 
is gathered. 
“To follow this method, it is requisite'well to observe the 
advancement of the season ; the shooting of the mulberry 
leaf, whether it is checked by cold : if again, the growth of 
the leaf is delayed, and that heat should soon after set in, and 
ripen it more quickly than was expected, as often occurs, it 
would be advantageous then to hasten the worms by heat; 
for if they are .allowed to delay from want of heat, their first 
age is prolonged, and the mulberry leaf will grow, and 
harden, and become unfit for them. The essential point is, 
that their progress should follow that of the mulberry leaf. If 
