SILK-WORMS. 
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about 367 feet square of wicker hurdles, and 
which consequently cannot produce more than 
240 pounds of cocoons (Fig 3.) ; they are only 
small, thirteen-feet-square rooms, containing in 
the middle four rows of double wicker hurdles 
placed one above the other, and about thirty 
inches wide. 
There are four ventilators in the ceiling, two 
fire-places in the two cross angles, and three ven- 
tilators in the walls, on a level with the floor. 
Each small laboratory has its barometer and two 
thermometers. I have not mentioned the as- 
pect of my laboratories, because all aspects are 
good, provided the air circulate freely every- 
where, and that there be a possibility of shading 
or shutting out the sun. I have them in all 
positions. 
The cleanliness of my laboratories is extreme ; 
there is no disagreeable smell of any sort, and it 
requires no perfume. The best is the natural 
aromatic fragrance of the mulberry leaf while the 
silk-worms are alive, and afterwards that of the 
cocoon when forming, or when formed. 
In case the season becomes very cold, as it hap- 
pened in 1813 and 1814, the fire-places may be 
used, not only to renew the air, but also to warm 
it, being careful in these instances to burn good 
large wood, which keeps the fire longer, and not 
