SILK-WORMS. 
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drawn from 1800 cocoons, which weigh 7 a pounds. 
This cocoon yields 1760 feet of spun silk ; the 
ounce of this spun silk is 264,000 feet long : 
421 feet 8 inches of the silk spun from the great 
cocoon of large worms of four casts, weigh a grain. 
This same cocoon yields grains of spun silk ; 
because, on an average, 11 ounces of silk are 
drawn from 750 cocoons, which weigh pounds. 
This cocoon consequently gives about 3885 feet 
of spun silk ; one ounce of this spun silk is 
242,880 feet long. 
It appears astonishing that the silk-worm in 
about three days, which it employs in forming 
the cocoon, should produce such an enormous 
length of silk ; and in this I do not include the 
first down which is taken off the cocoon, nor the 
coarse floss. 
We may conclude, on an average, that the silk- 
worm in forming the cocoon draws a thread of 
half a mile in length*. 
The proportions between good cocoons that 
have been pierced, and have been used for the pro- 
duction of eggs, and the remains which they con- 
tain, vary little. These cocoons cannot be spun, 
because the continuity of the thread has been 
broken by the moth. The empty cocoons are 
* In l’Abbe Rozier’s Cours d' Agriculture, it is stated 
that one single thread that has formed a whole cocoon is three 
miles long. 
