Real and supposed effects of igneous action. 351 
Il. Mr. Macture’s Letter. 
Remarks on the igneous theory of the earth, in a letter to 
the editor aloe Ss Maclure, dated Jalapa, Mexico, 
February 8, 18 
Dear Sir—Although M. Cordier sent me his essay upon 
the temperature of the interior of the earth, being at Har- 
mony when it arrived at Philadelphia, I had not seen it, until 
Tread the analysis of it in your Journal of October last. As 
in the pendulum, motion proceeds from one extreme to the. 
other, so it seems that our. moral faculties, as well as our 
takes appetites, must be stimulated by something extra, 
o afford pleasure, or satisfy curiosity ; sy having lately at- 
tended to the process of fire against water, I was a little sur- 
prised at the magnitude and saepentaiany of the proofs of 
the existence of this immense reservoir of melted. matter, 
occupying the earth’s centre, with all the operations of the 
molecules of heat perpetually radiating from it; my limited 
experience in the chopping of rocks, having almost convinced 
me that the two agents, fire and water, had been alternately 
at work, in covering the primitive, as I thought I could dis- 
cover rocks, with the volcanic. characters, alternating with 
the transition, secondary and alluvial. Perhaps, when any 
phenomenon can be‘accounted for by visible causes, subject 
to the evidence of all our senses, the inv of mysteri- 
ous and hidden agents to account for them, rather augments 
than removes the ans mee in which nature has veiled all 
her actions. The mon opinion of mankind, that the 
sun is the evident cause setok the heat of the earth, seems to 
agree with all experiments made by Perone, Seog and 
others, on the temperature of the ocean; (as you may see 
y some memoirs read before the French Paints by Perone, 
to be found in the Journal de Physique,) proving that heat ae 
creased in the exact ratio of the distance from the surface, un- 
til even under or near the equator, the thermometer descend- 
ed to two degrees above freezing, which, if I recollect well, 
corresponded with some experiments made on the waters of 
the lake of Geneva, and had induced me at one time to at- 
tempt experiments on our lake Ontario, but which | never 
had an opportunity of trying. At the time those theories 
