From St RO N't I AN. g 



and place it fo that it fhall cool flowly and v/ithout difturbance. 

 The ciyftals will be found attached to the infide of the veffel, 

 fhooting beautifully through the water to the length of an inch 

 or more. The form of the cryftal is abundantly diltindt ; it is 

 a thin quadrangular plate, which is fometimes fquare, though 

 more frequently a parallelogram ; the largeft of them feldom 

 exceed a quarter of an inch in length, and that is ufually fome- 

 what more than their breadth. Sometimes the edges of the 4^ 

 plates are plain, oftener they prefent two facets meeting like the 

 roof of a houfe. They, for the moft part, adhere to each other 

 in fuch a manner as to form a thin plate an inch or more in 

 length, and half an inch in breadth, the margin |being irregu- 

 lar from projeding redangles, the whole terminated by a regu- 

 lar cryflal. Sometimes the plates are thicker, and form folid 

 parallelopepids, and occafionally are feen perfecft cubes. 



19. In the courfe of expofure to the air for a few hours, 

 thefe cryftals ceafe to be tranfparent ; they become white, 

 powdery and effervefcent. The gain of carbonic acid does 

 not compenfate the lofs of humidity ; for they fuffer a dlminur 

 tion of weight which amounts to nearly 10 per cent. To pre- 

 ferve them, we muft have recourfe to phials very clofely corked. 

 When fubjedted to heat, they lofe the faperficial moifture with 

 a hiffing noife j as the heat approaches to near a dull red, they 

 undergo fufion, which feems to be of the watery kind ; for as 

 foon as all the humidity is diflipated, there remains a white 

 powder that refifts an extreme degree of heat. Water enters 

 largely into their compofitionj 100 grains of them loft by the 

 expulfion of the moifture, 68 grains. Water diflblves them but 

 flowly, particularly when they have not been bruifed, in the pro- 

 portion of 8.5 grains to the ounce at temperature 60. An 

 ounce of water, in a heat fufl&cLent to keep the folution boiling, 

 diflblved no lefs than 218 grains. This is an aftoniftiing degree 

 of folubility in an earthy matter, and affords a diftinguifhing 

 feature of Strontites. Thefe folutions are pofTeffed of all the 



Vol. IV. B properties 



f 



