Polytechnic Association. 819 



exact amount of steam required to do a given amount of work, 

 even though that amount should be varied every second. 



Early in the last century Evans sent to England the plan of his 

 direct pressure steam-engine, which was tried by Trevithick ; but the 

 English, for twenty years, scouted the idea of using high pressure 

 steam ; and would not probably have used it up to this day, had not 

 high power been required in small space for the locomotive. Many 

 other improvements in the application of steam were first made in 

 this country. For example, the use of two cylinders for applying power 

 continuously by cranks set at right angles to each other, invented by 

 Joseph Dixon, and used in about the year 1823. Perkins, who 

 made improved boilers, and Dr. Church, who made improvements in 

 the valve-gearing for steam carriages, went to England with their 

 improvements, and spent their lives there, in trying to put them in 

 practical operation. While in England the high pressure engine is 

 seldom used, except for locomotives, in this country ninety-nine out of 

 every 100 engines are high pressure ; and our engineers are convinced 

 that this will be the engine of the future. It requires less space, costs 

 less, and can be run with equal economy. 



A great many improvements have been made in the high pressure 

 engine. Mr. Charles T. Porter has invented a very sensitive governor 

 and other improvements. Of late, Mr. Porter has presented the 

 advantage, although he does not claim to have originated the idea 

 of high speed pistons. That it is economical to run a high pres- 

 sure engine at a very high speed, he claims is fully demonstrated by 

 the Allen engine. Upon that particular point, and the operation of 

 the Allen engine, President Barnard will now address you. 



F. A. P. Barnard, S. T. D., LL.D. (the president of the Ameri- 

 can Institute), premising that the paper was drawn up in the form of 

 a report to be formally presented to the managers of the fair of the 

 American Institute, for 1870, the investigation having been made at 

 •the request of Mr. Porter, one of the exhibitors of the Allen engine 

 in that year, read the following : 



HIGH SPEED ENGINES. 

 Eeport on the Allen Engine. 

 To the Managers of the Annual Fair of the American Institute, 

 for 1871 : 



The undersigned judges in Department Y, group 1, in said fair, 

 beg leave to submit the following report supplementary to their 

 report heretofore rendered in regard to the high speed steam engine, 



