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Microscopical Essays. 



and by which gold and filver is drawn to any degree of minute- 

 nefs. Every thread proceeds from thefe two refervoirs, but are 

 united afterwards ; fo that if it is examined by the microfcope, it 

 will be found to confift of two cylinders, or threads, glued to- 

 gether, with a groove in the middle ;' afeparation may fometimes 

 be perceived. 



When the filk-worm has found a convenient fituation, it fets to 

 work, firft fpinning fome loofe thread, which ferves to fupport 

 the future fuperflruclure ; upon thefe it forms an oval of a loofe 

 texture, confifting of what is called the flofs filk ; within this it 

 forms a firm and more confident ball of filk, remaining 

 during the whole bufinefs within the circumference of the fphe- 

 roid that it is forming, refting on it's hinder parts, and with it's. 

 mouth and fore legs directing and faflening the threads. Thefe 

 threads are not directed in a regular circular form, but are fpua 

 in different fpots, in an infinite number of zig-zag lines : fo that 

 when it is wound off, it proceeds in a very irregular manner,, 

 fometimes from one fide of the cone, then from the other. This 

 thread, when meafured, has been found to be about three hun- 

 dred yards long, and fo fine, that eight or ten are generally rolled 

 off into one by the manufacturers. The filk-worm ufually em- 

 ploys about three days in finifhing this cone; the infide is 

 generally fmeared with a kind of gum, that is defigned to keep 

 out the rain ; in this cone it affumes the pupa form, and remains 

 therein from fifteen to thirty days, according to the warmth of 

 the climate. When the moth is formed, it moiftens the end of 

 this cone, and by frequent motions of the head loofens the tex- 

 ture of the {ilk. fo as to form a hole without breaking it. 



When 



