318 INSECT ARCHITECTURE. 



The length of the unbroken thread in a cocoon 

 varies from six hundred to a thousand feet; and as 

 it is all spun double by the insect, it will amount to 

 nearly two thousand feet of silk, the whole of which 

 does not weigh above three grains and a half: five 

 pounds of silk from ten thousand cocoons is consi- 

 derably above the usual average. When we consider, 

 therefore, the enormous quantity of silk which is 

 used at present, the number of worms employed in 

 producing it will almost exceed our comprehension. 

 The manufacture of the silk, indeed, gives employ- 

 ment, and furnishes subsistence, to several millions 

 of human beings; and we may venture to say, that 

 there is scarcely an individual in the civihsed world 

 who has not some article made of silk in his pos- 

 session< 



In ancient times, the manufacture of silk was 

 confined to the East Indies and China, where the 

 insects that produce it are indigenous. It was 

 thence brought to Europe in small quantities, and in 

 early times sold at so extravagant a price, that it was 

 deemed too expensive even for royalty. The Emperor 

 Aurelian assigned the expense as a reason for re- 

 fusing his empress a robe of silk; and our own 

 James I., before his accession to the crown of Eng- 

 land had to borrow of the Earl of Mar a pair of 

 silk stockings to appear in before the English am- 

 bassador, — a circumstance which probably led him to 

 promote the cultivation of silk in England.* The Ro- 

 man authors were altogether ignorant of its origin, — 

 some supposing it to be grown on trees as hair 

 grows on animals, — others that it was produced by a 

 shell-fish similar to the mussel, which is known to 

 throw out threads for the purpose of attaching itself 

 to rocks, — others that it was the entrails of a sort of 



* Shaw's Gen. Zoology, vol. vi. 



