GEOLOGICAL. 187 



ing for breaks caused by denudation) about 840 miles ; 

 its thickness in this country averaging from six hundred 

 to eight hundred feet." 



" If all the points at which true chalk occurs," says 

 Professor Huxley, "were circumscribed, they would be 

 within an irregular oval of about three thousand miles 

 in long diameter the area of which would be as great 

 as that of Europe." 



You will observe in our specimens how nearly some 

 of these forms resemble the nautilus and the ammonite, 

 which in prehistoric ages lived harmoniously together, 

 before there was a man to look into their secrets with 

 a microscope, as we are at present doing ; now the 

 ammonite is extinct, and found only among the fossils. 



Thus you may see of what our ordinary building-stone 

 is formed. A bit of our church wall, which a few years 

 ago was erected, and a small chip of which I had prepared 

 for my cabinet, is a mass of corals. This stone is 

 called "Kentish rag." Here is another bit, from the 

 remains of the old Roman wall which was recently dis- 

 covered in digging for the foundation of a house in 

 Houndsditch, and which I went to inspect. There it had 

 been lying for about two thousand years. It is a mass 

 of marine animal remains. 



" Where is the dust that has not been alive?" 



And here is a chip from the Great Pyramid of Egypt, 

 that wonder of the world which, nobody knows how many 

 thousands of years ago, was erected, according to tradition, 

 by one hundred thousand men in twenty years. Six 

 millions of tons of stone is said to have been employed 

 in its construction, making it the most stupendous mass 

 of masonry in the world, its top reaching considerably 

 beyond the cross of the London cathedral church of St. 

 Paul's. It is a solid mass, you see, of animals called 



