194 
THE ART OF REARING 
greater than the floss obtained from cocoons 
formed in a temperature of 69°. This obser- 
vation may explain why the silk produced in 
very hot climates is stronger and less fine than 
that produced in temperate regions, where the 
silk-worms are reared at a lower degree of tem- 
perature. 
Art teaches us to avoid all the inconveniences 
of which we have spoken; inconveniences which, 
every year, destroy an enormous number of silk- 
worms, and tend to form a large proportion of 
defective cocoons. 
There are general and confused notions upon the 
diseases of silk-worms; but as the causes of those 
diseases have not been sufficiently investigated, it 
often happens that instead of a remedy, a poison 
is administered. 
The hygrometer and thermometer having shewn 
the causes of disease, also supply the means of 
curing them, and the means are those which I have 
recommended, fires in the grates in the angles of 
the laboratory, light-blazing fires now and tlien 
when required; opening the ventilators, fumigat- 
ing bottles, &c. &c. 
The fifth age is accomplished when the silk- 
worm pours out its silk, and forms the cocoon. 
The fifth age is perfected, when on touching the 
cocoon, it appears to have attained a certain con- 
