REPORT ON METEOROLOGY. 
223 
both philosophical and important, but which it appears to me 
has received fully its due share of commendation. 
Let us now see what experimental proofs we have of native 
heat below the invariable stratum. It is nearly a century since 
it was first suspected that the temperature of the earth increased 
as we descend. The proof however has been reserved for our 
own day, by the multiplication of observations which might 
annihilate every plausible objection,—for many such there 
undoubtedly are. Nor can we assert, that before the late re¬ 
searches of M. Cordier* * * § truth has decisively been made to ap¬ 
pear. The general consequences which have resulted from his 
inquiries, and which are substantiated by an abundant collection 
of facts observed in Cornwall, Saxony, Brittany, Switzerland, 
America, and other points, are as follow:—That the temperature 
of any stratum below that of invariability is absolutely the same 
all the year round f ;—That in all strata so situated the tempe¬ 
rature increases as we descend, without any exception ;—That 
though the results which have been obtained are far from giving 
the same law of increase for different countries, which from 
the imperfection of the observations it was impossible to expect, 
yet the general progression may be stated at from 25 to 30 
metres of descent for an increase of one degree centigrade, or 
from about 37 to 44 feet for one degree Fahr. J M. Cordier 
has elaborately and successfully refuted the idea that these 
effects could be produced by the lamps of the miners, though 
he has shown the nature and amount of the influence they 
actually exert. A more refined objection, imputing the heat to 
the condensation of atmospheric air descending into the mines, 
has been satisfactorily answered by Mr. Fox§, whose scientific 
observations on the mines in Cornwall, and especially on their 
temperature, and the electro-magnetic properties of their metal¬ 
liferous veins, promise so much towards the advancement of 
science. M. Magnus, whose register thermometer we have 
already alluded to, and who applied it to the present object, has 
* Annates du Museum d'Histoire Naturelle, 1827. See also Bulletin des 
Sciences Mathematiques, ix. Ill; Edin. New Phil. Journal, vol. v. & vi.; and 
De la Beche’s Manual of Geology (Introduction). 
f See proofs of this in Saxony, Annates de Chimie, xiii. 211, 
X M. Kupfferhas lately deduced 36°-81 English feet for 1°F. Poggendorff’s 
Annalen, xv. Edinburgh Journal of Science, April, 1832. The recent ex¬ 
periments of M. Gherard in Prussia, communicated by Baron Humboldt to the 
Academy of Sciences, give 180 feet of descent for 1° R. Bulletin de la Societe 
Philomathique, Mars—Avr. 1832. 
§ Philosophical Magazine, 1830. Both to Mr. Fox and to Mr. Hen wood we 
are indebted for some excellent original experiments. Edinburgh Journal of 
Science, vol. x. 
