PHYSICAL AND LITERARY. 35 



precipitated 28 grains of a reddifli pow- 

 der. 



E X P E R. XXIIL 



Twenty grains of fhell marie, cal- 

 cined in Experiment 2 1 . generated, with 

 the acid of fea fait, a confiderable degree 

 of heat, but without any effervefcence. 

 The unfoluble refidue weighed thirteen 

 grains, and the powder precipitated from 

 the filtered liquor, eighteen. 



Two circumftances, worthy of atten- 

 tion, occur in thefe experiments. The 

 one is, the abfence of effervefcence du- 

 ring the folution of the calcarious earth ; 

 the other is, the remarkable difference 

 betwixt the weight of fubllance carried 

 off from the marles by the acid of fea- 

 falt, and the weight of the powders after- 

 wards precipitated from that acid. 



Both thefe unufual appearances may. 

 be eafily accounted for from Dr Black's 

 ingenious experiments *. As to the firft, 



the 



* Edinb. Phyf. Fff. vol. II. Art.S, 



