46 ANNUAL OF SCIENTIFIC DISCOVERY. 



The duty established as a test of these engines is 600,000 pounds of water 

 raised one foot, with one pound of coal ; the water being measured by actual 

 discharge into the reservoir. The trials of the Hartford engine, gave, in 

 one case, 620,000, and in another, 690,000 pounds duty. 



The engines used at Cambridge, Mass., for working the pumps of the 

 water-works, have the following peculiarities : Two trunk engines work the 

 pumps by direct action, each combining the use of high and low pressure 

 steam. The high pressure cylinder is placed within the other, and, instead 

 of allowing the exhausted steam to escape, it is carred back through pas- 

 sages in the covering of the outer cylinder ; and made to enter this outer or 

 low-pressure cylinder at the same end as it enters the first; here it acts, 

 expansively, and is finally conveyed through the side supports of the en- 

 gine into the condenser. The piston of the outer cylinder is a ring, and its 

 power is transmitted by three piston-rods instead of one, which are bolted 

 to the same cross-head, or yoke of iron, as the single piston-rod of the inner 

 cylinder ; thus the powers of the two cylinders are combined to effect the 

 same object at the same moment. The inner cylinder is kept warm by the 

 steam in the outer one, and this again by a small quantity of steam which is 

 admitted for that purpose into its hollow cover or jacket. The diameter of 

 the small cylinder is twelve inches, and that of the large twenty-four inches, 

 its piston being a ring five inches wide. The plunger of each pump dis- 

 places about sixteen, and a half gallons of water each stroke. 



COAL-BURNING LOCOMOTIVES. 



Numerous abortive attempts have been made during the last ten years, 

 for substituting coal for wood as fuel for locomotives. When it is known 

 that all over Europe coke is used as successfully as wood is here, it is not 

 easy to understand why there should be any difficulty in using anthracite, 

 but practice has taught that there are many. There are now three different 

 plans before the public, and they are all approved by competent engineers. 

 A locomotive on the Baker plan has been constructed for the Providence 

 and Fall River Railway Company. The novelty consists in making the 

 flames follow a curved flue, instead of going straight to the chimney. The 

 smoke is thus more thoroughly mixed with air, and consequently better 

 burned. There is also an arrangement to supply the furnace with warm 

 air. It is alleged that the result will be a saving of fifty per cent. 



Another locomotive is in use upon the Hudson River rail-road, the 

 invention of A. F. Smith, Superintendent of that road. This machine 

 weighs 59,000 pounds, the driving-wheels are five feet in diamater, the 

 stroke is twenty-two inches, the boiler is forty-nine inches in diameter and 

 eleven and a half feet long. The barrel proper, extending from the flame- 

 sheet to the smoke-arch, is seven and a half feet long and forty inches in di- 

 ameter. There are 179 brass tubes, of two inches outside diameter and 

 seven and a half feet long. The fire box measures sixty by thirty-two 

 inches, with a combustion chamber extending four feet into the barrel of 

 the boiler. This chamber is divided by a water leg, extending from the 

 front of the fire-box to within twenty inches of the tube sheet. Around the 



