28 NATURAL HISTORY 
was low, and the common air was very cold, the fpirit rofe much 
at feveral depths in the well; but when the Spirit of the Thermometer 
ftood higher in the common air, the alteration was lefs : for Feb. 
25, 1702, (Experiment III.) when the Thermometer ftood two 
degrees below juft freezing, it rofe but five degrees, when fufpended 
at twenty-one feet, for half an hour; and March 10, 1702, (Expe- 
riment 8.) the Thermometer ftanding at two degrees below juft 
freezing, it rofe but feven degrees though fufpended at fixty feet for 
an hour; by which it is only plain, that the colder the Atinofphere, 
the greater is the difference between that and the more even tempe- 
rature of the air below in the well, and the Thermometer rifes 
higher, but not in any given proportion to the depth ; fo that what is 
here advanc’d cannot confirm the hypothefis now in queftion. That 
vapour, or moift fleam, rifes from all waters, and is indeed dif- 
perfed more or lefs in all places, not only in places open to the 
Atmolphere, but in the clofeft rooms and the deepeft cells of the 
earth, is certainly true: Water will eafily fly off” in evaporation, 
fometimes imperceptibly, oftentimes, and in cold weather more 
efpecially, vifible, as being condenfed into larger globules by the 
ambient cold ; and where there are fubterraneous heats occalioned 
by the fermentation of Pyrites, Sulphur, Salt, and fuch mineral pro- 
moters of warmth, there this evaporation is copious and extra- 
ordinary, but ftill not equal to the effect, to the plenteous ffreams, 
and even immediate rivers which proceed at once from the bowels 
of the earth in fome places ; neither is there reafon to fuppofe 
fuch fubterraneous heats every where and at all times, nothing being 
more uncertain and unequal, than the diftribution of fuch igniting 
mineral mixtures. Tis reafonable then to conclude, that the 
fubterraneous heats which either refult from the fermentations of 
mineral mixtures, or from the equal diftribution of fire through all 
matter,, are not fufficient where they are, nor conftantly enough 
found in any place, to fupply perennial fprings. The groundlefs 
fancy of a central fire, and that mountains are alembicks in which 
the vapours are collected and diftilled down their fides, is too chi- 
merical to need confutation. Again, That perennial fprings 
do owe their riie to rains and dews is difputed, and thought un- 
likely, becaufe they do not feem to be at all affe&ed by the excefs 
or deficiency of either, let us confider therefore the nature of 
fluids and the texture of the earth together, and fee whether 
perennial fprings may not principally be owing to the waters of 
the Atmofphere although neither increas’d by heavy rains, nor fen- 
fibly diminifhed by great droughts. 
ft he eai th muff not be looked upon as an absolute dry ma fs 
exhibiting here and there its wonders in pouring forth a fprin g 
or 
