THE STEAM-ENGINE. 



401 



cal force may be obtained, at least equal in amount to the former. A pint of 

 water, therefore, and two ounces of common coal, are thus rendered capable 

 of doing as much work as is equivalent to seventy-four tons raised a foot 

 high. 



The circumstances under which the steam-engine is worked on a railway 

 are not favorable to the economy of fuel. Nevertheless a pound of coke burned 

 in a locomotive-engine will evaporate about five pints of water. In their 

 evaporation they will exert a mechanical force sufficient to draw two tons 

 weight on the railway a distance of one mile in two minutes. Four horses 

 working in a stage-coach on a common road are necessary to draw the same 

 weight the same distance in six minutes. 



A train of coaches weighing about eighty tons, and transporting two hun- 

 dred and forty passengers with their luggage, has been taken from Liverpool to 

 Birmingham, and back from Birmingham to Liverpool, the trip each way ta- 

 king about four and a quarter hours, stoppages included. The distance be- 

 tween these places by the railway ia ninety-five miles. This double journey 

 of one hundred and ninety-miles is effected by the mechanical force pro- 

 duced in the combustion of four tons of coke, the value of which in England 

 is about five pounds. To carry in England the same number of passengers 

 daily between the same places by stage-coaches on a common road, would 

 require twenty coaches and an establishment of three thousand eight hundred 

 horses, with which the journey in each Direction would be performed in about 

 twelve hours, stoppages included. 



The circumference of the earth measures twenty-five thousand miles ; and 

 if it were begirt with an iron railway, such a train as above described, carry- 

 ing two hundred and forty passengers, would be drawn round it by the com- 

 bustion of about thirty tons of coke, and the circuit would be accomplished in 

 five weeks. 



In the drainage of the Cornish mines the economy of fuel is much attended 

 to, and coals are there made to do more work than elsewhere. A bushel of 

 coals usually raises forty thousand tons of water a foot high ; but it has on 

 some occasions raised sixty thousand tons the same height. Let us take its 

 labor at fifty thousand tons raised one foot high. A horse worked in a fast 

 stage-coach pulls against an average resistance of about a quarter of a hundred 

 weight. Against this he is able to work at the usual speed through about eight, 

 miles daily ; his work is therefore equivalent to about five hundred tons raised 

 one foot. A bushel of coals, consequently, as used in Cornwall, performs as 

 much labor as a day's work of one hundred such horses. 



The great pyramid of Egypt stands upon a base measuring seven hundred 

 feet each way, and is five hundred feet high, its weight being twelve thousand, 

 seven hundred and sixty millions of pounds. Herodotus states, that, in con- 

 structing it, one hundred thousand men were constantly employed for twenty 

 years. The materials of this pyramid would be raised from the ground to 

 their present position by the combustion of about four hundred and eighty tons 

 of coals. 



The Menai bridge consists of about two thousand tons of iron, and its height 

 above the level of the water is one hundred and twenty feet. Its mass might 

 be lifted from the level of the water to its present position by the combustion 

 of four bushels of coals. 



The enormous consumption of coals produced by the application of the 

 steam-engine in the arts and manufactures, as well as to railways and navi- 

 gation, has of late years excited the fears of many as to the possibility of the 

 exhaustion of our coal-mines. Such apprehensions are, however, altogether 

 groundless. If the present consumption of coal be estimated at twenty millions 



VOI,. II. 26 



