16 On the Progressive Increase of Temperature 
comes stationary at about 36° Fah. varies from two hundred to five — 
hundred fathoms. Below this there is probably no change of tempe- 
rature. M. Lenz found it to sink no lower as far down as one thou- 2 
sand fathoms; but we can expect no increase of temperature without 
a complete subversion of the law of nature, by which a —— = 
_of density is imparted to water. | 
It would appear, then, that the evidence at present is decidedly in i 4 
favor of a great central heat in the globe, even leaving out of consid- 
eration the easy explanation it affords of so many geological phenom- a 
ena. Buta new source of evidence has lately been opened, and one 
much less liable to objections than the high temperature of minesx— 
in the borings for water lately practised to such an extent in sia ; 4 
and Germany. @ 
It was an important observation of Mr. Fox, that the water whieh 4 
gushed out from springs at the bottom of the Cornish ape had al- 
ready the temperature of the air in the places where it and — 
was completely convincing as to the source of the heat so lone observ= | 
ed. The Artesian springs of the continent confirm his observation. 
In general, the water which flows from them is of a higher tempera- _ 
ture than the mean of the earth at the place, and is warmer as its — 
source is deeper. At Vienna forty or fifty have been formed, and 
the water of all has a temperature varying from 52° to 58°, 
mean temperature, according to Humboldt, being 50.549 F. “At 
Heilbronn in Wurtemberg, five borings.sunk to supply a paper mill 
to the depth of from sixty to one hundred and twelve feet, deliver 
water having a temperature of about 55°; and the proprietor has — 
taken advantage of it to warm his works in the winter, and succeed- — 
ed in keeping the apartments at a temperature of 46° when ae ol 
the air was 25° below zero of Fah. = 
There are, however, many exceptions and anomalies which are 7 
not to be wondered at, when we consider, a from the i * 
of the strata and other causes, the depth of the boring is no sure:in- a 
dication of the true level from which the water comes. It is only 
when we are sure beforehand of the nature of the strata, that we can 
come to correct conclusions in regard to the ‘true Tore of ae 
earth at any given de 4 
One of the most interesting of the exceptions we have met with, a 
and which illustrates best the nature of the anomalies we may expect | 
to meet with, is the case of a tube of three inches and a quarter in 
diameter, sunk to the depth of three hundred and thirty five feet at 4 
sek 
