4o6 ESSAYS and OBSERVATIONS 



turning green with the ol. tart* together 

 with the quantity of the clouds that pre- 

 fently formed, and the deepnefs of their 

 green, that it was very ftrong of the cha- 

 lybeate principle : I therefore fet the mix- 

 ture before the fire, to fee what change a 

 little heat would produce; and, when I 

 obferved that a fmall heat had no effect, I 

 gradually increafed the heat, till bubbles 

 appeared on the furface of the water; but 

 this oceafioned no change on the colour 

 of the water, the faint blue remaining 

 much the fame. I then conjeflured, from 

 the water not turning green with fyrup of 

 violets, as in the former experiments, that 

 there was a greater quantity of acid than 

 ufuat united to the chalybeate principle : 

 And, to difcover whether my fufpicion: 

 was right, I dropt into the fame glafs, 

 containing the water and powder of galls, 

 one or two gutts (I do not remember 

 which) of oL tart. ; and, having mixed 

 it by ftirring, it immediately produced a 

 very deep blue. 



FroiM this experiment, I think it ap* 

 fears, that a water may be very ftrong 



of 



