PHYSICAL ann LITERARY. 364 
ter not turning green with fyrup of violets, as 
in the former experiments, that- there was-a 
greater quantity of acid than ufual united to 
the chalybeate principle: and, to difcover 
whether my fufpicion was right, I dropt into 
the fame glafs, containing the water and pow- 
der of galls, one or two gutts ( I don’t re- 
member which) of ol. tart.; and, having 
_. mixed it’by ftirring, it immediately iy rota 
a ah deep blue. 
From this experiment, I think it appears, 
4 ame a water may be very {trong of the ‘cha- 
lybeate principle, and yet difcover very little 
of it by the common experiment with galls; 
fo that it may be proper always to try it with 
the ol. 7art.alfo: for the ftrergth of the iron- 
principle is,’as the colour:and quantity of the 
_ clouds formed by this oil; that is, if the 
_ clouds are of a light yellowifh colour and 
fmall in quantity, the chalybeate principle is 
weaker; if they are of adark brown and more 
in quantity, it is ftronger; if they are of a 
_ green colour, the: ‘deeper the green and more 
in quantity, the ftronger i is the chalybeate 
principle; which I have found to correfpond 
with truth, by répeated experiments, not on- 
ly on ‘this’ Spaw, but on foluticns of vitriolum 
ZL, Bi" % fyi ) - Martis 
Nie, 
on ell 
