From STRON'TIAN. 9 



and place it fo that it fhall cool flowly and without difturbance. 

 The cryflals will be found attached to the infide of the vefTel, 

 fhooting beautifully through the water to the length of an inch 

 or more. The form of the cryflal is abundantly dilUncTt ; 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 

 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 projed^ing redlangles, the whole terminated by a regu- 

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

 parallelopepids, and occafionally are feen perfedl 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 diminu- 

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

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

 When fubjeded to heat, they lofe the faperficial moifture with 

 a hifling noife ; 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 diffipated, there remains a white 

 powder that refifts an extreme degree of heat. Water enters 

 largely into their compofition j 100 grains of them loft by the 

 expuliion of the moifture, 68 grains. Water diffolves 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 fufficient to keep the folution boiling, 

 difTolved no lefs than 218 grains. This is an aftonifhing degree 

 of folubility in an earthy matter, and affords a diftinguilhing 

 feature of Strontites. Thefe folutions are pofTefTed of all the 



Vol. IV. B properties 



