914 Transactions of the American Institute. 



the indicator that the impulsea correspondod in length to the pres- 

 sure in the cylinder at that instant ; the sum of these impulses being 

 registered by appropriate gearing. This was an approximate solu- 

 tion of the problem ; but it gave the sura of inclined instead of 

 vertical ordinates ; and for this reason, as well as in the imperfect 

 recording of tlie ratchet, was inaccurate. A perfect instrument for 

 this purpose would find a large sale, as it would determine the aver- 

 age power exerted for any given time without the necessity of 

 extensive calculations. It would be used to determine the power 

 used for different processes, that used by tenants ; and it would be 

 possible with it to tell exactly how many foot pounds of force was 

 exerted in driving a vessel from New York to Liverpool. The inven- 

 tion described by the Chairman is not what is really wanted. 



Mr. J. K. Fisher said that about 1858 he invented an instrument 

 just as described, and showed it at the Novelty Works in this city, 

 with a view to get them to manufacture it. It was tliought it M'ould 

 work well, but that the demand for such instruments was too small to 

 warrant the outlay incident to tlie introduction of a new one. It 

 was a combination of the steam indicator with a counting apparatus, 

 similar to that in Morin's counting dynamometer. A plate is vibrated 

 by the cross-head motion ; against this plate a small friction- wheel is 

 held by a spring-axle ; the piston of the indicator pushes this wheel 

 beyond the axis of vibration of the plate when the pressure is posi- 

 tive, and draws it within the axis when the pressure is negative, as 

 in the case of a condensing engine on its back stroke. In case of a 

 high pressure engine, the back pressure on the return stroke is 

 deducted by tlie backward motion of the plate. It has been said 

 that the friction of the wheel on the plate tends to prevent a true 

 indication of the pressure ; but it may also be said that the friction 

 of the pencil on the paper has a like tendency, and probably may 

 cause as much inaccuracy as would attend the wheel if the instrument 

 were well designed and executed. The American Institute miglit 

 find advantage in getting snch an indicator to test engines at the 

 fairs ; using the common indicator and other test at the same time. 

 As there is some inexactness in all known tests, it is well that they 

 should be used to check each other. 



Mr. Babcock remarked that Mr. Fisher's invention was one more 

 added to the list of inventorg of this instrument. But the o})inion of 

 the Novelty AVorks given ten years ago in regard to the demand for 

 an indicator like this, would not hold good at the present day. The 



