Scientific Lectuhes. 189 



was unknown, and instead of tliem, an enbankment was made 

 around the structure, as an inclined plane of earth, both of which 

 were raised up, as each successive course of stone was laid, 

 and when the structure was completed this earth was removed. 

 The strong mortai-s and cements of the Romans were unknown. They 

 had to depend for the stability of their walls upon the massiveness of 

 the stone, and the close fitting of the joints. This great pyramid, 

 with a base of 700 square feet, and 450 feet high, contains 6,500,000 

 tons of stone, and the embankments would have required more than 

 50,000,000 tons of earth. You will be better able to realize these 

 figures when I repeat that all of the masonry on the Erie canal amounts 

 to but 2,500,000 tons, or but one-third of that used in this great ]>yra- 

 mid, and that all of the earth which was moved to construct the 360 

 miles of that canal, or for the 500 miles of the Erie railway, or even 

 for the 2,000 miles of the Pacific railway, each of them only equaled in 

 quantity, that which was probably used, in the place of scaffolding, 

 to hoist and lay the stone of this pyramid. Herodotus says that 

 100,000 men were engaged for ten years in building this earthen 

 causeway, and that the same number of men were engaged for twenty 

 years longer in laying up the masonry. My own calculations show 

 that these statements cannot be far wrong, and you will observe that 

 they do not include the workmen who were employed in quarrying, 

 cutting, and transporting the stone, &c., which would have quadrupled 

 the number. This great work required the labor of 500,000 men for 

 thirty years, and at the present value of such labor in such countries, 

 would have cost $5,000,000,000. A modern engineer would construct 

 such a work for $100,000,000, and with a tithe of the men. He would 

 quarry the stone by steam drills, load them with steam cranes, 

 transport them on the ISTile with steam-yessels, and on land with loco- 

 motives. Instead of 50,000,000 tons of earthen embankments, costing 

 $10,000,000, he would apply a few hoisting machines, and with a 

 score or two of men, would deliver the stone to the hands of the 

 masons, as fast as they could lay them. I will give one other example 

 and comparison with ancient engineering. The Amphitheater or 

 Coliseum of Home was finished in the golden period of the profession, 

 in the year 79. It was an oval, and enclosed and covered an area of 

 six acres. The structure weighed half a million of tons, and could 

 seat 70,000 persons. The contrast with this building may be made 

 by referring to the exhibition buildings of London and Paris. The 

 London building was 1,848 feet long, and 450 feet wide, and sixty-o^ne 



