ON THE FACTS OF EARTHQUAKE PHENOMENA. G7 
The opinion, that active volcanoes are only the outlets for these internal 
workings, or as it were, the chimneys, not of particular fires scattered here 
and there, but of enormous volcanic furnaces existing in the depths beneath, 
has of late been distinctly enunciated by the most eminent geologists and 
observers of volcanic phenomena.” 
Again, hear Humboldt :—‘It is only by considering these various rela- 
tions under a general point of view, and following them on a large extent of 
the surface of the globe, through formations of rocks the most different, that 
we are led to abandon the supposition of trifling local causes, strata of 
pyrites, or of coal set on fire.” (Per. Nar. vol. iv. p. 47.) 
Steffens, on the other hand, in his ‘Geognostich. Geologische Aufsetze,’ 
p- 325, finds in such combustibles “the condition, sine gua non,” of volcanic 
action ; and it is strange how the same crude notion of the necessity for a 
combustible besets almost every author down to the present day, forgetful 
that cosmical fire needs no fuel, that the perpetual evolution of heat from 
the interior of a planet (without anything being burnt away) is no more 
wonderful, than (nay, is only in analegy with) the perpetual evolution of 
light and heat from the fixed stars and sun, which no one supposes to be 
flaming fires. See on this Humboldt in his ‘ Pers. Nar.’ vol. i. p. 257. 
The whole question of the chemical reactions, conjecturable as occurring 
within the active volcanic foci, has been ably discussed by Gay-Lussac, in his 
‘ Reflections sur Volcans,’ in Annales de Chim. et de Phys. tom. xxii. p. 415, 
which paper contains the germ of nearly everything that has been since ad- 
vanced upon the subject, clearly and succinctly given. 
Thus, then, ignorant as we are of all within the outer surface or skin of 
our globe (and of how much of its exterior, for the ocean shrouds two-thirds 
of it from our eyes!), we are compelled to see the close connexion of these 
mighty heating powers in which tgnition is present on the vastest scale, yet 
without combustion, with the forces of terrestrial electricity and magnetism ; 
forces which are those alone, that within range of our observation are mu- 
tually convertible, and both convertible into heat. 
Currents of both we know are ever passing with variable activity through 
enormous volumes of the earth’s crust, the different parts of which possess 
very different conducting powers. Can it be that these currents, constrained 
to pass through narrow and bad conductors, at vast depths, in some formations, 
ignite them in their progress? Will it be found that the great lines of vol- 
canic activity (as dreamed of by Bylandt) are in some way connected with 
those of terrestrial magnetism? are possibly normals to the surface curves 
of equal magnetic intensity? A glance at one of Gauss’s magnetic maps, 
and at another of the great bands of active volcanoes on our planet, almost 
forces the mind into such conjectures. } 
If, then, as seems at least possible, there be a direct connexion (still more, 
if this be one of cause and effect) between volcanic action and those forces of 
electricity and magnetism whose cosmical relations we are just beginning to 
get glimpses of; and if, again, these are modified.and possibly determined in 
their extent and laws of action by the astronomic motions of the earth, and 
by its variable reception of heat from the sun, and dissipation thereof again 
in the celestial spaces; it must result that the volcano and the earthquake are 
not independent of the laws which determine climate and regulate the vicis- 
situdes, and the limits of perturbation, of the seasons. 
It is perhaps the most wonderful circumstance in the history of our globe, 
that its mightiest agencies interdepend, upon a balance so precise, that per- 
turbations in any one of the forces, so small as to appear to us at first sight 
perfectly insignificant, would, if continued or not corrected, be sufficient 
totally to alter or disarrange the vast machine. We can prove this in some 
