Its surface was composed of a great number of metals, such as potassium and sodium, which have the peculiar property of igniting at the mere contact with air and water; these metals kindled when the atmospheric vapours fell in rain upon the soil; and by and by, when the waters penetrated into the fissures of the crust of the earth, they broke out into fresh combustion with explosions and eruptions.

Such was the cause of the numerous volcanoes at the origin of the earth." "Upon my word, this is a very clever hypothesis," I exclaimed, in spite rather of myself.
"And which Humphry Davy demonstrated to me by a simple experiment.

He formed a small ball of the metals which I have named, and which was a very fair representation of our globe; whenever he caused a fine dew of rain to fall upon its surface, it heaved up into little monticules, it became oxydized and formed miniature mountains; a crater broke open at one of its summits; the eruption took place, and communicated to the whole of the ball such a heat that it could not be held in the hand." In truth, I was beginning to be shaken by the Professor's arguments, besides which he gave additional weight to them by his usual ardour and fervent enthusiasm.
"You see, Axel," he added, "the condition of the terrestrial nucleus has given rise to various hypotheses among geologists; there is no proof at all for this internal heat; my opinion is that there is no such thing, it cannot be; besides we shall see for ourselves, and, like Arne Saknussemm, we shall know exactly what to hold as truth concerning this grand question." "Very well, we shall see," I replied, feeling myself carried off by his contagious enthusiasm.

"Yes, we shall see; that is, if it is possible to see anything there." "And why not?
May we not depend upon electric phenomena to give us light?
May we not even expect light from the atmosphere, the pressure of which may render it luminous as we approach the centre ?" "Yes, yes," said I; "that is possible, too." "It is certain," exclaimed my uncle in a tone of triumph.

"But silence, do you hear me?
silence upon the whole subject; and let no one get before us in this design of discovering the centre of the earth.".