138 TRANSACTIONS OF THE [FEB. 1, 



but did not have moving parts. Newcomen found great diffi- 

 culty in liaving his engine tried at the tin mines to pump water. 

 It was not automatic. A boy was employed to turn the faucet, 

 for the introduction of steam into the cylinder to raise the piston, 

 which lowered the pump rods on the other end of the walking- 

 beam; the boy then closed this faucet, and turned another for 

 the injection of water to condense the steam, thus forming a 

 vacuum beneath the piston when the air pressure depressed the 

 piston, raising the pump rods and the water. At first the con- 

 densing water surrounded the cylinder, and the engine was very 

 slow in action; a leak occurring, the strokes of the engine were 

 much increased, and caused alarm at the rapidity. This led to 

 the water injection pipe. Humi)hrey Potter, a boy employed to 

 tnrn the faucets, soon grew tired of his work, and invented and 

 applied some levers and strings to oi)en and close the faucets, 

 tlnis rendering the engine automatic, and increasing its speed 

 and safety. 



Beigliton improved the inventions of Potter, making them a 

 jjart of the mechanism. 



In 17G3, James Watt, a philosophical-instrument maker, 

 entered the employ of the University of Glasgow. Tlieir model 

 of Newcomen's engine had been sent to London for repairs, and 

 he induced the faculty to have it returned so that he could study 

 and repair it. He was well versed for his time in the principles 

 of latent heat, having studied under Dr. Black, and was able to 

 appreciate the enormous loss of heat caused at each stroke by 

 heating and then cooling the cylinder. He designed the separate 

 condenser and air pump, thus avoiding the cooling of tlie cylin- 

 der, and introducing greater economy in the amount of fuel con- 

 sumed. 



His specifications in his patent of 17G9 for the construction 

 of engines are still models for study in principles. In mechan- 

 ical execution he encountered difficulties which we cannot 

 appreciate, Avith our present plants for constructing work of 

 almost any size. 



Newcomen's engine is now represented by tlic Cornish pump- 

 ing engines. 



Watt converted the reciprocal motion into rotary motion, 

 making a motor for general purposes. This is represented to- 

 day by the marine condensing engine. 



Ideas respecting locomotion were develo})ing on every hand; 

 and while many are willing to ascribe the invention of the loco- 

 motive to one man, the ])robabiliLies are that it was due to many 

 minds, as we know its constj-uction has been. Watt patented, 

 in 17G9, a steam carriage, but did not construct one. 



Cugnot's locomotive of 1769 would run for a few minutes. 



