1086 Transactions of the American Institute. 



The curve thus found is always exterior to that derived from Mari- 

 otte's law, as seen in Fig. 7, which is a diagram fully developed in 

 accordance with the foregoing directions, and with both curves of 

 exi3ansion delineated. Several diagrams from various engines, com- 

 pared in the foregoing manner are appended to illustrate the prin- 

 ciple. 



At the close of this important paper, a gentleman referred to the 

 method of estimating the area of the diagram by cutting it out of 

 paper and weighing it. The weight of a square inch of the same 

 kmd of paper being known, the area of the indicator diagram is easily 

 calculated. This method has been recently brought into notice as 

 somethmg "very novel.'' It is, however, to be found in some very 

 old works on mensuration. It gives very accurate results, but 

 requires the aid of a very delicate chemical balance. Common scales 

 will not answer. 



Adjourned. 



