“Every one present this evening,” and the lecturer gave an embracing wave of his hand, “knows of the singular aberrancy in the rotational motion of the earth, which has been often geographically described as the ‘wobbling of the poles.’ Astronomers have proven a real tipping of the poles alternately to one side, and then to the other, a swaying of the poles like the recurrent oscillations of a top as it ‘goes to sleep.’ But this swaying in the earth’s case is periodic and unchanging. It is sometimes rather abrupt, and at other times the tipping is regulated and progressive; but it is established, and has had a generally accepted explanation, in the attraction of the swelling equatorial prominence of the earth by the sun and moon, while suggestions have also been made that it was due to internal shiftings of mass, or to changes of exterior weightings, through the alternate and variable formation and melting of polar snows. “But it has in the light of the present theory of the pear-shaped earth a new and rather startling explanation. “We are, however, this evening, not so much concerned with the broader cosmic aspects of this state of affairs, as with the immediate consequences to the permanence of our land surfaces. “The mechanics of this condition and its possible effectiveness in developing contrary placed zones of rupture can be easily conceived. This awkwardly conditioned sphere, revolving upon a shorter diameter--revolving also with astonishing velocity--and bearing at either extremity of its longer axis unequal masses, is obviously in a state of peripheral strain, that is, it is in strain at such distances from either of the disproportioned ends, the one in the south seas, the other in the desert of Sahara, as would represent the more or less sharply sloping surface from its average rotundity, towards these oblique extremities. “Gentlemen,” the speaker seemed excitedly rushing into danger, but with a fixed expression, aimed somewhere at the blank and uninfluential physiognomies at the back of the hall; like that of an engineer who can neither restrain nor reverse the speed which may either carry him safely over a tottering support or plunge his train to the bottom of the gulch; “Gentlemen, the Isthmus of Panama is in this zone; _the Canal is there_!” this last reminder uttered with no very reasonable deliberation, “and it is to my mind an absolutely established certainty, that the secular instability of that region, shown by geological investigation, will again become apparent; and”--he raised his voice with a kind of exhalation of defiance, as if he spurned equivocation and invited denial--“and, it will become apparent with increased violence.