3. The Mesozoic or middle period of life.
4. The Neozoic or recent period of life.
These are all subdivided again, and other words more difficult to spell are introduced into science, thus crowding out the vulgar herd who cannot afford to use the high priced terms in constant conversation.
Old timers state that the primitive condition of the earth was extremely damp. With the onward march of time, and after the lapse of millions of years, men found that they could get along with less and less water, until at last we see the pleasant, blissful state of things. Aside from the use of water at our summer resorts, that fluid is getting to be less and less popular. And even here at these resorts it is generally flavored with some foreign substance.
{Illustration: THE MASTODON.}
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.