C 456 ] 
EXPERIMENT VIII. 
After being acquainted with the preceding expe- 
riments, you will not wonder that the Tourmalin 
afforded the fame appearances on removing it, in the 
open dry air, from the fun-fhme into the {hade ; 
and again, from the (hade into the fun-fhine. 
If thefe fmall differences, in the degrees of warmth, 
are capable of caufing fuch appearances ; well may 
the greater differences; and flich more particularly as 
Mr .Brawn and yourfelf have experienced in freezing 
of Quick- filver : and therefore I cannot now agree with 
you in calling that the natural Jlate of the Tourmalin , 
which arij'es from the heat given it by boiling water . 
EXPERIMENT IX. 
It appears by the preceding experiments, that when 
the Tourmalin was of the fame temper with the air 
in the different rooms, there were no electric figns to 
beobferved. From which we may underftand, if 
the heat of the air fhould be increased, even beyond 
that of boiling water, a Tourmalin expofed therein 
for a time, would afford no eledtric figns ; that is, 
whilft the flone continues of the fame temper with 
the air. I have lately caufed the heat of the air to be 
increafed, in a convenient room, beyond the degree of 
vital heat, even to 108 : and then placed two Tour- 
malins, in the fame room, very near the Thermometer , 
without being able to obferve any eledtric effedts ; that 
is, after they had remained therein a {hort time. 
E X- 
