280 PHILOSOPHICAL TRANSACTIONS. [aNNO 1751. 



and a greater number in proportion. He had tried several numbers of shieves as 

 far as 36 ; but 20 seemed to be the largest number that will answer well in 

 practice. A very commodious tackle of 1 2 might be executed in wood, in the 

 same manner that common blocks are made. 



In constructing a tackle of 20 for 3 tons, the larger tier of shieves should not 

 be less than 8 inches, the running line need not be thicker than half an inch 

 diameter, and the iron pins need not be so thick- 



LXXXIII. On some Vegetable Balls. By IVm. Dixon, Esq. F. R. S. of Lover- 

 sail near Doncaster in Yorkshire, with Remarks on them by Mr. IVilliam 

 Watson, p. 498. 



These balls seem to be plants of a very particular kind. They were taken up 

 in a fresh- water lake, on a large common in the East Riding of Yorkshire, about 

 12 miles west of Hull. The lake is from 100 to 200 acres in size, according to 

 different seasons, and empties into the Humber ; which is pretty salt, and has 

 sometimes infected it a little at very high tides. The water is very bright, and 

 the bottom in many places is quite covered with these balls, like a pavement, at 

 different depths. These now sent were about 6 inches under water ; and many 

 are left quite dry every summer. On this communication Mr. Watson observes, 

 that the vegetable here mentioned, he has never seen before ; neither had he 

 been able to find it described in any of the botanic writers he consulted. The 

 matter of which it is composed, is that of a conferva ; and should therefore 

 have had a place under that genus in Dillenius's Historia Muscorum. They are 

 of a deep green mossy colour, are hollow, of an irregularly spherical figure, and 

 of different sizes, from an inch an half to 3 inches in diameter. They are co- 

 vered with very short villi externally, and the thickness, from their external to 

 their internal surface, is about a quarter of an inch ; their texture is most com- 

 pact the nearest to the surface. He denominates them globose conferva. Mr. 

 Ray, in his History of Plants, vol. 1. p. 83, describes a plant, which he found in 

 Sicily, something like this now sent by Mr. Dixon. 



LXXXIV. Of the Copper-Springs in the County of IVichlow in Ireland. By 

 the Rev. Henry Kenroy, D. D. p. 500. 

 These mines lie in the southern part of the county of Wicklow, on each side 

 of the river Arklow, and about 7 miles west from the town of that name, among 

 hills that rise to the height of small mountains. The mine, which was formerly 

 wrought, is that of Ballymurtogh, on the south bank of the river. It yielded 

 vast profit to the undertakers; but it has been disused for some years past. 

 This is amply compensated by the far richer mines of Crone-Bawn, on the north 

 side of this river. 



