234 PLYMOUTH INSTITUTION. 



hollow tube of gold which surrounded it will cohere and remain 

 suspended. In this manner sixteen ounces of gold, which would 

 not occupy more space than one cubic inch and a quarter, will com- 

 pletely gild a wire sufficient to encompass the whole globe of the 

 earth. 



The lecturer here brought forward an interesting account of the 

 attempts which had been made to manufacture silk from the web of 

 the spider. 



" In the early part of the last century the attention of the Royal 

 Academy of Sciences at Paris was called to a memoir of M. Bon, 

 on the silk which he obtained from the bags in which the common 

 house spider deposits its eggs. These bags were carded and spun 

 into thread, and a few small articles, such as gloves and stockings, 

 were made from it, rather as objects of curiosity than use. The fur- 

 ther investigation of the subject was committed, by the Academy, 

 to M. Reaumur, who, after many trials, gave it as his opinion that 

 this kind of silk could never be worth collecting, on account of the 

 small quantity yielded by each spider — its great inferiority in lustre 

 to that of the silk worm — the impossibility of making the spiders 

 live in quiet with each other, and the great difficulty of providing 

 them with suitable food. 



The project of obtaining silk from spiders lay accordingly aban- 

 doned for several years : very recently, however, it has been revived 

 by Mr. A. B. Rolt, of Friday Street, London, who has made a com- 

 munication on the subject to the Society of Arts, for which they 

 have awarded him their silver isis medal. 



The species of the insect to which Mr. Rolt turned his attention 

 is the common garden spider, (aranea diadema,) the webs of which, 

 in autumn, are so conspicuous on the surface of shrubs, and in other 

 similar situations. 



On allowing one of the animals to crawl over his hand, he found 

 that it drew a thread with it wherever it went : he likewise, without 

 any difficulty, wound some of this thread over his hand, finding 

 that the spider continued spinning while the thread was winding 

 up. On this hint, he connected a small reel with the steam engine 

 of the factory in which he is occupied, and putting it in motion at 

 the rate of 150 feet per minute, found that the spider would thus 

 continue to aftbrd an unbroken thread during from three to five 

 minutes. 



A specimen of this silk, which accompanied Mr. Rolt's commu- 

 nication, was wound off from twenty-four spiders in about two 

 hours. Mr. Rolt estimates its length at about 18,000 feet. Its 



