276 



THE POPULAR SCIENCE MONTHLY. 



in such districts. Its great economical advantage over animal power, 

 its freedom from liability to become disabled by epizootic diseases, 

 its reliability under all circumstances, and the many other advantages 

 which are possessed by the machine, are already securing its introduc- 

 tion, despite the difficulties arising from popular prejudice and unfa- 

 miliarity, from hostile municipal laws and other existing obstacles. 



We are learning that this motor, when it can be used at all, is com- 

 paratively inexpensive ; that our roads are improved by it ; and that 

 the ancient idea of its conflicting with the interests of owners and 

 workers of horses is only a superstition. 



Fig. 40. Hancock's Steam-Carkiage, 1833. 



Such a commencement having been made, it is difficult to conceive 

 how great may not be the future of this branch of industry when the 

 valley of the Mississippi and our Western plains, the natural habitat 

 of this motor, shall have become finally a principal seat of its manu- 

 facture as well as of its employment. 1 



69. The steam-blast of Hackworth, the tubular boiler of Seguin, 

 and the link-motion of Stephenson, constitute the essential features 

 of the modern locomotive. Locomotives have gradually and steadily 

 increased in size and power from the date of their introduction. 

 The Rocket, which first proved conclusively, in 1829, the value of 

 steam-locomotion, weighed 4 tons. In 1835 Robert Stephenson, 

 who had constructed it with his father, writing to Robert L. Ste- 

 vens, said that he was making his engines heavier and heavier, and 

 that the engine of which he inclosed a sketch weighed nine tons, 

 and could draw " 100 tons at the rate of sixteen miles an hour, on a 

 level." Locomotives are now built weighing seventy tons, and power- 

 ful enough to draw more than 2,000 tons at a speed of twenty miles 

 an hour. The modern locomotive consists of a boiler, mounted upon 

 a strong light frame of forged iron, by which it is connected with 

 the wheels. The largest engine vet constructed in the United States 

 is said to be one in use on the Philadelphia & Reading Railroad, hav- 

 ing a weight of about 100,000 pounds, which is carried on twelve 

 driving-wheels. A locomotive has two steam cylinders, either side 

 1 Vide paper by the author, Journal of the Franklin Institute, 1871. 



