io SEC TION MECHANICS. 



In order to illustrate the way in which the system of kinematic 

 analysis, which I have sketched to you, can be applied to actual 

 machines, Professor Reuleaux has examined analytically an immense 

 number of those unfortunate devices called rotary engines, on which 

 so much ingenuity and excellent brainwork has been wasted. In his 

 " Theoretische Kinematik," he gives illustrations of between sixty and 

 seventy of these machines, analysing every one of them into one or 

 other of the three chains which we have been examining (Figs. 3, 4, 

 and 6). The inventor has generally called his machine " rotary " 

 because of some notion that there were more rotating parts, or more 

 direct rotation, than in the ordinary engine. While there are a few 

 engines in which this is the case, in the vast majority it is entirely a 

 mistake. Here is one (see Fig. 1 1) which hasbeen invented over and over 

 again. I believe it was invented for the first time in 1805, by a Mr. 

 Trotter ; it was re-invented in 1831, 1843, 1863, 1866, 1870, 1872, 1873, 



Figure n. 



and possibly at many other times. One gentleman, whom I see here, 

 told me he had invented it himself twenty years ago ! After all, it is 



