324 PHILOSOPHICAL TRANSACTIONS. [aNNO 1747. 



lived together till April ; when he gave one of them away. After this separation, 

 the fish that remained was so affected, that for 3 weeks it would eat nothing he 

 could give it ; so that fearing it would pine to death, he sent it to the gentleman 

 on whom he had bestowed its companion ; and on being put together again, it 

 eat immediately, and recovered its former briskness. 



A Supposition hoio the fVhile Matter is produced, which Floats about in the jiir 

 in Autumn. By the same. N° 482, p. 428. 



Mr. Arderon having lately a large spider in his hand, by chance he let it fall, 

 and it hung by its thread, as they very commonly do. On holding his hand very 

 still it readily ascended up it again, and thus by giving it a shake, and then hold- 

 ing his hand still, the spider ascended and descended a great many times. He 

 thought at first it had spun a new thread at every descent, and was desirous to 

 have measured how long a one he could cause it thus to spin; but on a stricter 

 examination he very plainly perceived, that whenever it ascended, it wound its 

 thread with its feet into a sort of coil, and when it descended only ravelled it 

 out again. 



The manner how they perform this is diverting enough: but as spiders may be 

 had almost in every place, and the experiment is so easily tried, he only adds, 

 that as these coils of thread are exactly like those floating in the air towards the 

 end of summer, he thinks it is not improbable those are made in the same 

 manner, when spiders have a mind to direct their course in the same direction 

 their threads lie. 



Remarks on the Precious Stone called the Turquoise. By Cromwell Mortimer, 



Sec. R. S. &c. N" 482, p. 429. 



This stone has received its modem name of Turchesia, and Turquoise, from 

 its being most commonly brought from Turkey into various parts of Europe. 

 De Boodt* says, the colour of this gem is a variegation of green, white, and 

 blue; and that there are two sorts of it, the oriental, from the East-Indies and 

 Persia, and the occidental, from Spain, Germany, Bohemia, Silesia, &c.; that 

 in Persia, where it is found in greatest plenty, it adheres to black stones, as if it 

 were an excrement or a transudation from them. A stone of this sort is seldom 

 found to exceed a walnut in size ; and he mentions one in the great duke's mu 

 seum, on which the head of Julius Caesar is engraved, as a very extraordinary 

 sample; he adds, that he never saw one larger than a hazel-nut; that some of 

 the oriental ones have the faculty of preserving their colour perpetually, which 

 are called stones of the old rock; and that others lose their colour gradually, and 



• Gemmar. et Lap. HUt. — Orig. 



