8o OF STONES, 



fpar, with an admixture of fulphur, \ve have a great abundance, 

 The largeft and faireft I have fcen are in the ftrata of clay above 

 the bridge of Simonburn ; where they lie in all directions, foft and 

 fragil, not enduring to be touched but with the greateil gentle- 

 nefs, yet, when expofed to the air, acquiring the hardnefs of a 

 marble, and capable of a politure. Their exterior colour, when 

 wafhed and freed from the clay, is grey, or a yellowifh-white. 

 Sometimes they have an elegant indented incruflation, and 

 ibmetimes an incruflation with minute protuberated points, of a 

 greyifh-black ; both the indentings and points numerous. They 

 are filvery and glittering when broke. Some of them exhibit a 

 curious phenomenon by politure, the grit of one appearing 

 very white, and that of another of a dark lead colour, inclining 

 to black, owing to metalline admixtures. The radiated heads 

 of others being taken down by politure, they exhibit beautiful 

 clouds of grey and white, owing to the fame caufe. In the fire 

 they crackle and burft, mewing their gloffy foliaceous texture. 

 Rubbed hard upon a ftone they fmell like burnt horn. Their 

 jlne, from the center to the circumference, are formed to hold 

 their joints together like futures. Their central tubull or perfo- 

 rations are filled with various matter, as hard as their own fu fa- 

 glance, and of different colours, taking their interior figure and 

 circular channels. 



The Belemnit* are of all fizes, from lefs than an inch to ten 

 inches ; fome of them cylindric ; others comprefTed, with a lon- 

 gitudinal furrow on one or both fides ; fome with fmall tuber- 

 cles ; and others with their joints a little raifed. They are rarely 

 found conic, and thofe not exceeding two inches in length, 



The Entrochoi are from lefs than half an inch to fix inches, but 

 it is with difficulty they can be had entire of fo great a length ; 



the 



