544 PHILOSOPHICAL TRANSACTIONS. [aNNO ]6Q3, 



mantum aemulae. The figures are taken from certain very clear and transparent 

 stones found in England, of a constant shape. They are called, in some ancient 

 leases of royal mines, rough or mineral pearl ; understanding probably by the 

 word pearl, any thing that was resplendent and bright, and particularly figured 

 like a drop of water, which these stones have of themselves naturally, some of 

 them being exactly spherical, others like a half globe, others like a half oval, 

 with an edge raised on the top. 



Their natural polish is not to be counterfeited, but very easy to be distin- 

 guished by a microscope from the artificial polish of glass and crystals. These 

 stones are of the pebble kind, that is, not to be calcined by simple fire ; whereas 

 most other figured stones are calcinable with a very easy fire. They are very 

 hard and solid, and do not consist within of laminae or flakes, but break 

 every way with great difficulty, and naturally throughout smooth. As they are 

 of a very different nature and texture from all other ombriae I ever yet saw, 

 and have no vestigia of any spinas in any part of them, they may be concluded 

 to be stones of their own kind ; and though they are in shape like some of the 

 ombriae, yet they will not come, I think, within the suspicion of having been 

 animal substances. 



I am not averse to think, after so manifest and considerable discoveries of 

 this kind, as Augustino Scilla had made in Sicily, that most of the ombriae 

 have been echini. It is remarkable, there are but two or three echini yet disco- 

 vered either in ours or the Mediterranean Sea. But of the ombriae of Europe, 

 besides these present anomalous stones, there are at the least 20 species, figured 

 and described by Aldrovandus, Augustino Scilla, Dr. Plot, &c. and in vast 

 quantities in most counties of England. 



^n Account of Virginia, and a Voyage thither. By Mr. John Clayton, Rector 



of Crofton, at Wakefield in Yorkshire. N° 201, p. 781. 



The air and temperature of the seasons are much influenced by winds in 



"Virginia, both as to heat and cold, dryness and moisture. The N. and N. W. 



are very nitrous and piercing, cold and clear, or else stormy. The S. E. and S. 



hazy and sultry hot ; their winter is a fine clear air, and dry, which renders it 



very pleasant ; their frosts are short, but sometimes so very sharp, that it will 



freeze the rivers over 3 miles broad ; it freezes there the hardest, when from a 



moist S. E., on a sudden the wind passing by the N., a nitrous sharp N. W. 



blows, not with high gusts, but with a cutting brisk air ; and those vales then 



that seem to be sheltered from the wind, and lie warm, where the air is most 



stagnant and moist, are frozen the hardest, and seized the soonest, and the 



fruits are there more subject to blast than where the air has a free motion. Snow 



