270 SECTION MECHANICS. 



mechanisms hitherto adopted. Looking at the models by them- 

 selves, some of them seem extremely intelligible, and some very 

 much the reverse. I shall endeavour, in the very limited time 

 at my disposal, to point out the leading ideas which run through 

 the whole, and connect the very familiar mechanisms with those 

 more complex ones which, although differing only in degree from 

 the former, appear at first sight so entirely dissimilar. 



In the old books upon machinery, such as that of Ramelli for 

 instance (1588). each machine was taken up by itself, and treated as a 

 whole from beginning to end. One kind of pump after another, for 

 example, may be described without any recognition of their essential 

 identity, or the use of any single word to express the concept pump. 

 Each machine is described' separately as an apparatus which raises water 

 from such a place, in such a way, and delivers it at such a place. The 

 complex idea which we cover by the word pump, had not yet found a 

 place in the writer's mind. 



Presently it was found, of course, that machines were not all different 

 from beginning to end, but consisted of various combinations and 

 repetitions of similar elements ; these elements in time became more 

 distinctly recognised, and were called mechanisms. Each machine 

 accordingly was not now described as a whole, but was analysed into 

 the mechanisms of which it consisted, and these received separate 

 treatment. Very much valuable matter has been written upon 

 machinery from this point of view. In our own country, Professor 

 Willis especially gave most valuable contributions to the science of 

 machinery on this basis. Hitherto, however, we have stopped at this 

 point. We have obtained each mechanism " somehow," but have not 

 yet troubled ourselves as to how it was invented, or what the elements 

 were. We have, that is, analysed the machine into mechanisms, but we 

 have not yet analysed the mechanisms themselves. We are all familiar 

 with the interesting and valuable work which has been done in the way 

 of examining the motions of particular pieces or members of a mechanism 

 after it has been presented to us, but it cannot be denied that in all cases 

 the mechanism itself has been in the first place taken as a whole. 



Professor Reuleaux has attempted to perform the final analysis 

 to which I have alluded, and to discover of what elements mechanisms 

 consist, and how these elements have been combined. He starts 



