23^ 



NATURE 



\yuly 13, 1876 



for this name may have been subsequently given to it. 

 Again, "The bow of the archer is a machinal organ in which 

 energy is stored; the sensible force of the muscles is 

 made latent in it, and it is this latent energy stored in the 

 elastic bow which actually propels the arrow. In the 

 ballista and catapult this principle receives still more 

 extended application, for in them kinematic means are 

 employed to store the energy of many men, so as to 

 employ it concentrated with correspondingly increased 

 effect. Later on the same principle extends itself to 

 primary forces, and it is to-day more used than ever, from 

 the tiny watch-work or the spring of a gun-lock, through 

 innumerable mechanisms, up to the Armstrong accumu- 

 lator or the air-vessels of the Mont Cdnis borers." But it 

 is from the kinematic point of view that the progress of 

 the development of the machine is most accurately mea- 

 sured. What is the fundamental characteristic of the 

 improvement that has been effected in the various stages 

 of advance in the development of a machine? Prof. 

 Reuleaux answers : " The line of progress is indicated in 

 the manner of using force-closure or more particularly in 

 the substitution of pair closure and the closure of the 



Fig. 7. 



kinematic chains obtained by it for force-closure." In the 

 fire-drill, which is an early form of turning-pair, we 

 have not only force-closure by the action of the hands 

 in the longitudinal direction, previous to the intro- 

 duction of the bearing-piece on the top, but also force- 

 closure in the transverse direction by the hands. The 

 invention of the string for turning the drill, itself a great 

 advance, introduces another kinetic pair of elements, but 

 still the string is constrained to keep in contact with the 

 stick by the force- closure of the tension produced by the 

 hands. In the earliest form of lathe with double head- 

 stocks, the force-closure of the double element is changed 

 to pair-closure, marking a great advance in the develop- 

 ment of the machine, and the string is worked in a more 

 definite manner by one end being fastened to a bow or 

 spring- beam, whilst the other is worked by the foot (Fig. 5). 



" Thus simplicity or fewness of parts does not itself 

 constitute excellence as a machine, but increased exact- 

 ness in the motions obtained, with diminished demands 

 on the intelligence of any source of energy." 



In more recent machinery, such as Newcomen's engine 

 (Fig. 6), we see the connection of the beam D and the 



pump-rod E, affected by the force-closure of the weight 

 F acting on the chain, the connection of the piston C, and 

 the beam D, afifected by force-closure also, by the same 

 weight, whilst the valve-gear was worked by hand. 



By the invention of his nearly perfect parallel motion, 

 Watt introduced kinematic pair and chain-closure into 

 the steam-engine, as well as by the introduction of auto- 

 matic valve-gear. Space will not permit us to give an 

 account of the systems of kinematic notation proposed by 

 Prof. Reuleaux, but it certainly is one of the most im- 

 portant chapters in the book, and will well repay a careful 

 study, although some little time and trouble is evidently 

 required to get the meaning of the various symbols im- 

 pressed on the memory. When this has been done we 

 have no doubt that it will amply compensate the learner 

 for his pains, by the much more ready comprehension 

 he will obtain of complex mechanisms. We can only 

 say, in the words of our author, " The reader need not 

 fear that any continual alteration of his accustomed ideas 

 will be demanded from him in making himself familiar 

 with the system of contractions. For a scientific symbolic 



•Fig 8. 



notation is in essence nothing else than a systematised 

 method of contraction — it is not a hieroglyphic system 

 mysterious to the uninitiated." Under the head of ana- 

 lysis of chamber-crank chains, the various disc-engines, 

 rotatory engines and blowers, of which such a larj^e and 

 varied assortment has been from time to time invented, 

 are described and figured, and our author states at the 

 end of the long list so formed that the whole of the forms 

 that have appeared are probably not exhausted, and that 

 " a comparison of the machines described shows, indeed, 

 that there are many easily constructed inversions of exist- 

 ing mechanisms which have not yet been proposed, 

 and many analogies to existing forms which have 

 not been tried ; so we may look forward still to the pro- 

 duction of whole series of chamber-crank trains by the 

 never- resting empirics. In Chapter xi, we come to the 

 machine considered as a combination of constructive 

 elements and the complete enumeration of them, and 

 their systematic classification deserves particular atten- 

 tion. As an example of this classification we may give 

 the double-acting ratchet train (Fig, 7) and the double- 



