The earth's crust is variously estimated in the matter of thickness. Some think it is 2,500 miles thick, which would make it safe to run heavy trains across the earth anywhere on top of a second mortgage, while other scientists say that if we go down one-tenth of that distance we will reach a place where the worm dieth not. I do not wish to express an opinion as to the actual depth or thickness of the earth's crust, but I believe that it is none too thick to suit me. Thickness in the earth's crust is a mighty good fault. We estimate the age of certain strata of the earth's formation by means of a union of our knowledge of plant and animal life, coupled with our geological research and a good memory. The older scientists in the field of geology do not rely solely upon the tracks of the hadrasaurus or the cornucopia for their data. They simply use these things to refresh their memory. I wish that I had time and space to describe some of the beautiful bacteria and gigantic worms that formerly inhabited the earth. Such an aggregation of actual, living Silurian monsters, any one of which would make a man a fortune to-day, if it could be kept on ice and exhibited for one season only. You could take a full grown mastodon to-day, and with no calliope, no lithographs, no bearded lady, no clown with four pillows in his pantaloons and no iron-jawed woman, you could go across this continent and successfully compete with the skating rink. There would be but one difficulty. Tour expenses would not be heavy. The mastodon would be willing to board around, and no one would feel like turning a mastodon out of doors if he seemed to be hungry; but he might get away from you and frolic away so far in one night that you couldn't get him for a day or two, even if you sent a detective for him. If I had a mastodon I would rather take him when he was young, and then I could make a pet of him, so that he could come and eat out of my hand without taking the hand off at the same time. A large mastodon weighing a hundred tons or so is awkward, too. I suppose that nothing is more painful than to be stepped on by an adult mastodon. I hope at some future time to write a paper for the Academy of Science on the subject of “Deceased Fauna, Fossiliferous Debris and Extinct Jokes,” showing how, when and why these early forms of animal life came to be extinct. A Wallula Night. I have just returned after a short tour in the far West. I made the tour with my new lecture, which I am delivering this winter for the benefit, and under the auspices, of a young man who was a sufferer in the great rise-up-William-Biley-and-come-along-with-me cyclone, which occurred at Clear Lake, in this State, a year ago last September.