Proceedings of the Polytechnic Association. 953 



fact, that the governor was subject to considerahle fluctuations, and 

 consequently changed the point of cnt-ofF incessantly. 



The next and last table is of most interest as showing the rapidity 

 of the regulation, or, in other words, the amount to which the speed 

 of the respective engines varied under loads changed very suddenly 

 from extremely light to extremely heavy and vice versa. The strips 

 of telegraph paper marked by the means above described, as also all 

 the diagrams produced by the indicator, were severally inscribed with 

 a number or letter, by which they could be easily designated, and a 

 corresponding number or letter being entered in a large sheet of 

 notes kept for the purpose, allows the precise time, pressure, load, and 

 every other important fact relating thereto, to be ascertained with 

 certainty. A mark with colored pencil was also made on the tele- 

 graph strips at the moment an order was given to change the load, 

 the color blue or red indicating whether the load was put on or taken 

 off. The method of applying the load was to weight the lever, G, 

 to about as great an amount as one man could conveniently lift, and 

 to allow an active man first to raise the lever and hold it at a consid- 

 erable elevation, and then at a given signal to suddenly bring it 

 down, adding to it the whole weight of his body, and holding it 

 down until another signal should induce a return to the first position. 

 The engine would of course, when suddenly lightened, move quicker 

 than its proper rate, and when it had taken time to nearly or quite 

 recover, a sudden increase of load would reduce its speed below the 

 proper velocity. The greater load in the largest engine in the fifth 

 experiment was due to the placing of two men instead of one upon 

 the lever. One engine, it will be observed, was more subject to 

 increase than to decrease of motion under these circumstances, while 

 the other was faulty in the reverse direction ; the difference being 

 due to peculiarities in the governors and valves, and in the connec- 

 tions of these elements, which was very dissimilar in the two engines. 



After an interesting discussion on testing engines the Association 

 adjourned. 



January 13, 1870. 



Prof. S. D. Tillman, in the chair; C. E. Emeky, Esq., Secretary. 



The following notes on applied science and new discoveries were 

 presented by the chairman : 



