60 DISCOURSE ON THE STUDY 



(51.) The Menai Bridge, one of the most stu- 

 pendous works of art that has been raised by man in 

 modern ages, consists of a mass of iron, not less than 

 four millions of pounds in weight, suspended at a 

 medium height of about 120 feet above the sea. 

 The consumption of seven bushels of coal would 

 suffice to raise it to the place where it hangs. 



(52.) The great pyramid of Egypt is composed of 

 granite. It is 700 feet in the side of its base, and 500 

 in perpendicular height, and stands on eleven acres 

 of ground. Its weight is, therefore, 12,760 millions 

 of pounds, at a medium height of 125 feet ; conse- 

 quently it would be raised by the effort of about 

 630 chaldrons of coal, a quantity consumed in some 

 founderies in a week. 



(53.) The annual consumption of coal in London 

 is estimated at 1,500,000 chaldrons. The effort of 

 this quantity would suffice to raise a cubical block of 

 marble, 2200 feet in the side, through a space equal 

 to its own height, or to pile one such mountain upon 

 another. The Monte Nuovo, near Pozzuoli, (which 

 was erupted in a single night by volcanic fire,) 

 might have been raised by such an effort, from a 

 depth of 40,000 feet, or about eight miles. 



(54 ) It will be observed, that, in the above state- 

 ment, the inherent power of fuel is, of necessity, 

 greatly under-rated. It is not pretended by engineers 

 that the economy of fuel is yet pushed to its utmost 

 limit, or that the whole effective power is obtained 

 in any application of fire yet devised ; so that were 



labour is about 4 Ibs. of coals. The extreme toil of this ascent 

 arises from other obvious causes than the mere height. 



