356 ESSAYS anv OBSERVATIONS 
pofition, I diflolved alum in water, and that 
in a greater proportion, than it can be in: this 
Spaw, and then droptintoit o/. tart. p. d. ; there 
enfued no effervefcence, or fenfible change 
upon the water ; but a few air-bubbles ga- 
thered at the bottom of the glafs; nothing, 
however, in comparifon of what appeared 
when the o/. tartar. p. d. was dropt into the 
Spaw ; and no more than what formed upon 
dropping o/. tart. p. d. into a glafs of pure 
river-water. 
g. As chalybeate waters, in feveral parti- 
culars, refemble a folution of vztrzolum Martis 
in water, hence many have been induced to 
think, that thofe waters contained a vitriolum 
Martis {uch as is prepared by art: but fome 
of the lateft, and moft learned authors, as 
Hoffman, Everbaave, Sc. are of a contrary o- 
pinion, and fer a very good reafon, becaufe no 
vitriolum Martis could ever be found, upon 
evaporation of chalybeate waters: the expe- 
riments however made on this Spaw, feem to 
prove that it contains a fixed vitriol of iron ; 
for it not only turns green, upon the addition 
of ol. fart. (10).), but likeways, upon eva- 
poration, there is a falt left, which has all the 
properties of vitriolum Martis. 
