Report of Superixtendent. 65 



every liour. Indicator diagrams were taken from botli ends of the 

 cylinder every fifteen minutes. 



The representatives of the two rival engines from Providence, 

 cordially accepted the invitation to watch the experiments, and 

 accompanied my assistant in taking all the data. The dynamometer 

 indices were on the level of the shaft, twelve feet from the floor, and 

 were read with an opera-glass, which was passed from one to another, 

 and by agreement no reading was recorded until all were satisfied of 

 its Correctness. By this means the oflicial log corresponded exactly 

 with the memoranda of the opposing exhibitors, no errors could 

 occur, and collusion was impossible. 



[The two engines from Providence were of the same size, and 

 were run at the same speed. The results are, therefore, strictly com- 

 parable and are given in detail. The other engines were smaller and 

 of difterent sizes, so the results possess less general interest, and are 

 omitted in this publication.] 



TABLE 1^0. 1. 



Shovmig the principal data from the records and diagrams Tcejyt and 

 taken during the competitive trials of the non-condensing steam 

 engines at the American Institute Exhibition of 1869. 



Time. 



a. Date of experiment, 1869 



Duration of experiment, hours 



Engine. 

 5. Diameter of cylinder, inches 



c. Stroke of piston, inches 



Proportion of piston displacement in clear- 

 ances and ports 



Total revolutions 



d. Revolutions per minute 



e. Mean steam pressure in main pipe, pounds 

 Mean initial pressure in cylinder per indi- 

 cator, pounds 



f. Point of cut off in fractions of a stroke per 



indicator,' pounds 



Mean terminal pressure in cylinder per in- 

 dicator, pounds 



g. Mean efi'ective pressure outb'd end of 



cylinder, per indicator, pounds 



Mean effective pressure inb'd end of cylin- 

 der, per indicator, pounds 



[Inst.] 5 



