346 SOLID PARTS OF ANIMALS. ^ 



fine red colour. When pure it is insoluble in water, but it dis- 

 solves in alcohol, ether, fixed and volatile oils. When treated 

 with chlorine or sulphurous acid, it becomes of a very light yel- 

 low or almost colourless. 



From the observations of Reaumur, it would appear that va- 

 rious colouring matters are found in silk. For he mentions white, 

 yellow, brown, and green silk. 



6. The fatty matter and resin from yellow silk are obtained 

 mixed with the colouring matter. When the mixture of the two 

 is exposed to a gentle heat, the fatty matter first melts, and then 

 the resin. If we agitate the mixture with a little alcohol, and 

 then evaporate, the resin separates in stripes, and leaves the fatty 

 matter alone dissolved in the alcohol. 



The fatty matter and resin are soluble in alcohol, ether, fixed 

 and volatile oils, but not in water. They are specifically lighter 

 than water, and their colour is grey. 



CHAPTER XXX. 



OF SPIDER'S WEBS. 



THE spider, as is universally known, carries in the abdomen a 

 peculiar liquid, which it is capable of protruding from a number 

 (usually five) of mammillated eminences. This liquid hardens as 

 soon as it is emitted, and adheres so firmly to everything with 

 which it comes in contact, that it cannot be separated without 

 rupture. This is what constitutes the web of the spider. Every 

 thread of the web consists of several very minute threads adher- 

 ing together. Spiders are oviparous, and they enclose their eggs 

 in a cocoon of much stronger thread than that of which their 

 webs are made. These cocoons may be winded like those of the 

 silk-worm, and M. Bon of Montpelier first showed that spider's 

 silk is as strong and as beautiful as that of the silk-worm. In 

 1710 he published the processes by which he collected this silk, 

 wove it and dyed it of various colours ; and he assures his read- 

 ers that it is in no respect inferior to the silk from the silk-worm.* 

 In consequence of the account given by M. Bon, Reaumur was 



* Phil. Trans, xxvii. 2. 



