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THE POPULAR SCIENCE MONTHLY. 



Fig. 23. Leopold's Papin Engine, 1720. 



gested by Papin. It consists of two single-acting cylinders, r s, receiv- 

 ing steam alternately from the same steam-pipe through a " four-way- 

 cock," and exhausting into the atmos- 

 phere. We find no evidence that this 

 engine was ever built. 



When, during the last century, 

 the steam-engine had so far been 

 perfected that the possibility of its 

 application to other purposes than 

 the elevation of water had become 

 generally recognized, the problem of 

 its adaptation to the propulsion of 

 carriages was attacked by many en- 

 gineers and inventors. 



As early as 1759, Dr. Robison, 

 who was at the time a graduate of the 

 University of Glasgow, and an ap- 

 plicant for an assistant professorship 

 there, and who had made the ac- 

 quaintance of the instrument-maker, 

 James Watt, when visiting the work- 

 shop, called the attention of the 

 latter, who was probably then more 

 ignorant of the principles of the steam-engine than was the young 

 student, to the possibility of constructing a carriage to be driven 

 by a steam-engine, thus, perhaps, setting in operation that train 

 of thoughtful experiment which finally earned for Watt his splendid 

 fame. 



46. Watt, at a very early period, proposed to apply his engine to 

 locomotion, and contemplated using either a non-condensing engine, 

 or an air-surface condenser. He actually included the locomotive-en- 

 gine in his patent of 1784, and his assistant, Murdoch, in the same 

 year, made a working-model locomotive 

 which was capable of running at a rapid 

 rate. 



This model, now deposited in the 

 Patent Museum, at South Kensington, 

 London, had a flue-boiler, and a "grass- 

 hopper" engine. Its steam-cylinder 

 was three-quarters of an inch in diam- 

 eter, and had two inches stroke of pis- 

 ton (Fig. 24). The driving-wheels were 

 nine and a half inches in diameter. It 

 is reported to have run six to eight miles 

 an hour, its little driving-wheels making from two hundred to two 

 hundred and seventy-five revolutions per minute. 



Fig. 24. Mokdoch's Model, 1784. 



