SILK-WORMS. 
*139 
as much benefit as if the air were drier. When it 
circulates freely, and is of a gentle temperature, it 
does not become so easily charged with moisture. 
The thermometer will then shew whether the 
temperature of the laboratory may not require a 
fire of large wood, to maintain the degree of heat 
appointed for this age, which is the most im- 
portant. 
In our climate the deficiency of damp air never 
can occur. To absorb the great evaporation of 
fluid which constantly exhales from the silk-worms, 
the leaves, &Ct, the air should be invariably dry. 
If north winds prevail during the existence of 
the silk-worms, and particularly in the fifth age, 
it is rare to see them fail, even in the hands of the 
most ignorant peasants, because the dry air ab- 
sorbs the moisture exhaling from the worms and 
the leaves, and draws it off. This air penetrates 
thoroughly even into closed rooms, and absorbs 
the moisture of all substances, because it has a pe- 
culiar power of attracting water, as we may con- 
stantly experience in our houses. 
I have observed that the greatest losses in silk- 
worms, under the care of ignorant cultivators, oc- 
cur in the fifth age, by reason of the air becoming 
damp from the prevalence of some south w'ind, 
which is fatal to the silk- worms. The insects 
are thus plunged in hot vapour, which quickly 
•weakens them, checks their transpiration, and 
