504 



MEMOIR OF DANIEL TEEADWELL. 



equal to the depression which would be produced by a force equal to such weight acting horizontally 

 through u, in a direction from right to left. 



When this instrument is used, the plate a a a is fixed firmly upon a car, its face in a vertical plane, 

 and the cylinder bb filled with oil thiougli the stop-cock on the top, while the piston is at the bottom. 

 For greater accuracy in the measurement, the piston rod could pass through the bottom of the cylinder in 

 a close collar, so that the contents of the cylinder would be constant. Tliis addition to the rod is indi- 

 cated bv the dotted line. The rod h is then attached to the tender of the locomotive. As the piston 

 passes downward, the oil beneath it must flow through the small hole at c, and likewise between the walls 

 of the cylinder and the piston ; the resistance to its passage is in proportion to the square of its velocity. 

 Hence the arm cannot be depressed so suddenly beyond the mean pressure of the draft of the engine ; 

 its vibrations are controlled by the passage of the oil at the same time that the resistance to the slow pas- 

 sage of the oil is very inconsiderable. One hundredth of an inch between the side of the piston and the 

 cylinder, and one eighth of an inch diameter of the hole in the piston, gave a sufficiently slow movement, 

 even with a weight of two or three hundred pounds on the top of the piston rod. Any force required to 

 drive the oil through the narrow apertures has no practical influence on the result. 



The road on which these experiments were made comprises 20. \ miles of the eastern end of the Bos- 

 ton and Worcester road (now Boston and Albany) ; namely, from the depot in Boston to that in Framing- 

 ham, and consists of twenty-six different planes, horizontal and inclined, no inclination exceeding 

 thirty feet in a mile, and the longest inclination being 13,200 feet. There are, moreover, curves in its 

 course, the radii varying from to feet. The rails are common English edge rails of equal 



depth, of wrought iron, and weighing fifty-six pounds per yard ; they are fixed in iron chairs on wooden 

 sleepers [ties]. Immediately preceding the time of the experiment the rails had been adjusted, and the 

 road was in good order throughout. 



The following enumeration cxhiliits, under their respective names, the dimensions of the most im- 

 portant parts of the locomotive engines used in the experiments. 



Number of cylinders 



Diameter of cyHnders 



Length of stroke 



Steam way opened by the slide valve. 



Length of boilers and tubes 



Number of tubes 



Diameter of tubes 



Area of tubes inside 



Area of fire grate 



Area of boiler exposed to radiant heat 

 Weiglit of the enjrine when full of water 

 Diameter of hind and driving wheel 

 Diameter of journals (gudgeons) . . 



Diameter of forward wheels 



Diameter of journals of forward wheels . 



Height of chimneys 



Diameter of chimneys 



Meteor. 



Mercury. 



Lion. 



2 



11 in. 

 16 in. 



7 ft. 8J in. 

 70 



2 in. 



291 sq. ft. 

 7.6 sq. ft. 

 30.3 sq ft. 

 22,531 lb. 

 5 ft. 



4 1 in. 



42 in. 

 42 in. 



12 ft. 6 in. 



13 in. 



The same tender was used in all the experiments. The weight of this when empty was 5,680 lb. ; 

 it held 5,830 lb. of water; consequently, when full, its weight was 11,510 lb. 



being less than that of the fii-st, and noting the distance run by the force of gravit.v. He found the value of tlie friction, and 

 other resistances, to be efiual to the weight multiiili(Hi by the total lieight the train has descended, Jivick-d liy the distance run. 

 A number of experiments on the Liverpool and Manchester railroad, with weights averaging 60.5 tons, and a velocity of ten or 

 twelve miles an hour, gave an average resistance of 8.5 pounds to the ton of 2,240 pounds. — W. 



