360 ESSAYS anv OBSERVATIONS 
olum Martis, which were of a paler green 
than the artificial. 
In Augufi 1752, this Spaw, with fyrup of 
violets, {truck no green tincture. 
_ Wiru ol. tart. p. d. it immediately tarned 
green, and clouds of a deeper green and more 
in quantity than in Auguft 1750, were form- 
ed, and that much fooner than in the precee- 
ding experiments. 
WiTHu powder of galls it fcarce changed 
its colour; and, even after ftanding fome 
time, it exhibited but a faint blue. I was at 
a lofs for the reafon of its giving fo faint a 
blue with galls; when, at the fame time, I 
knew, by its immediately turning green with 
the o/. zart., together with the quantity of 
the clouds that prefently formed, and the 
deepnefS of their green, that it was very 
ftrong of the chalybeate principle: I there- 
for fet the mixture before the fire, to fee 
what change a little heat would produce; 
and, when I obferved that a {mall heat had 
no effect, I gradually increafed the heat, till 
bubbles appeared on the furface of the water; 
but this occafioned no change on the colour 
of the water, the faint blue remaining much 
the fame. I then conjectured, from the wa- 
ter 
