Experiments and Obfervations. 593 
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tance from that body, muft be refpe&ively four, nine, 
fixteen times lefs denfe. The fame thing may be faid of 
heat. 
Being willing to afcertain this truth by a final experi- 
ment, I placed feveral thermometers, whofe balls were 
not painted, at different diftances from the flame of the 
lamp, and expected to find, when the thermometer at 
four inches cli fiance was i° above that placed at eight 
inches dillance, the thermometer placed at two inches dif- 
tance fhould be 4 0 higher. But upon trying this experiment 
various times, placing the thermometers at different dif- 
tances from the flame of the lamp, and making the pro- 
per calculations agreeable to thofe diftances, it appeared, 
that the intenfity of the heat did not decreafe exadlly in 
the duplicate proportion of the diftances from the flame 
of the lamp, but fhewed a very odd irregularity. It 
feemed to- decreafe falter than the duplicate proportion of 
the diftances for the fpace of two inches and a half or 
three inches, after which it decreafed much flower. 
Whether this effect may be attributed to fome different 
ftate of the air’s purity at different diftances from the 
flame of the lamp, or to the vapours proceeding from 
the flame, I cannot take upon me to determine. 
The 
