84 REPORT—1840. 
129. Most intimately connected with the subject of subter- 
ranean temperature is that of the temperature of springs, which 
connects itself so remarkably with chemical, geological, and 
meteorological considerations. It is impossible not to adopt 
the idea, that the temperature of spring-water depends on the 
depth whence it takes its origin, since we now know, beyond 
any doubt, that up to a certain point at least, the heat of the 
strata increases as we descend; nor is there the slightest reason 
to suppose that this progression undergoes any considerable 
variation down to the (comparatively) moderate depth at which 
water would boil, however much we may feel the necessity of 
caution in inferring the actual condition of the earth’s nucleus. 
The subject is one of so much extent, that we must refer gene- 
rally to the works which specifically treat of it, amongst which 
that of Prof. Bischoff, of Bonn*, is the most important in our 
present point of view. According to him, the temperature of a 
spring is an index simply of the thermal condition of the 
stratum whence it takes its origin, or at least derives its chief 
heat. 
130. A very ingenious application of these principles has been 
made by Prof. Kupffer, and he has illustrated them by an ap- 
plication to observations of the temperature of two springs at 
slightly different elevations, near Edinburgh, made at differ- 
ent seasons of the yeart. By observing the annual range of 
temperature of the spring, its depth is known by Fourier’s 
formula, the conductivity of the soil being assumed from 
Leslie’s experiments. The retardation of epochs is also an 
index of the depth. Now the actual difference of level of the 
points of exit of the two springs being given, the difference of 
temperature due to height above the sea is known. The actual 
Very contrary results on the latter point, derived from springs, appear in M. 
Arago’s report on a recent French expedition, under command of Capt. Du- 
Petit-Thouars (Annuaire, 1840, p. 296), from which the ground would seem to 
be sometimes 4° cent. colder than the air.— Nov. 1840. 
* Die Warmelehre des Innern unsers Erdkérpers, 8vo. Leipzig, 1837. 
Some part of this work has been translated in the Edinburgh Philosophical 
Journal. It consists of four parts, containing 27 chapters, and is full of re- 
search and important information. 
+ These observations, published anonymously in Prof. Jameson’s Journal in 
1828, were made by me. I have only lately found that they have been sub- 
jected to an ingenious and searching analysis, first by Kamtz (Météorologie, 
li. 190) afterwards by Kupffer (Poggendorff’s Annalen, xxxii. 280), and 
made to yield results which, in making them, I could not have contemplated. 
This is one instance out of many, for the encouragement of young observers, 
showing that observations conducted on system, carefully and perseveringly 
made, and complete so far as they go, may afterwards prove of unexpected 
importance. 
