laS 'ConJb-uHion of afelf-msving WJjeeL 



work *. If the fteel face of C A be iippermoft, and the end C be fixed to C B, the extre- 

 mity A will rife from B, when the temperature is elevated ; and if the fuccceding bars be 

 fimiiarly fixed above each other, as in the figure, the whole fyftem will occupy a greater 

 length, or elevation, above C B, when heated, than when cold. Another more convenient me- 

 thod of difpofing the bars is (hewn in fig. 3 ; in this, the bars are fixed together at the middle, 

 with the brafs faces turned towards each other. Each bar has a flight curvature (much lefs 

 than is here (hewn), which will be increafed by heat, and by that means caufe the diftance be- 

 tween the middle of two extreme bars to be greater than it would be at a lower temperature. 



Thefe caufes of aftion may be applied to machinery by various contrivances, fome of which 

 fcrve toincreafe the length of range, but add nothing to the power. This laft, no doubt, is an 

 objedt of convenience, according to the efFecl intended to be produced. The only method of 

 adding to the power will confift in increafmg the number of the bars. Fig. 4, reprefents a 

 fyftem for this purpofe, which is the fimpleft and moft convenient that has occurred to me. A C 

 reprefents the circumference of a barrel, refembling thofe in which the main fprino-s of clocks 

 are put ; the length and diameter of which may be varied, according to the power intended to 

 be gained. To this external part is fixed a ratchet-wheel to receivp the click C, which 

 confines its motion to one direction. At A is fixed a plate to receive the aclion of the ex- 

 panfion-pieces. B D is an internal cylinder of the fame kind, which is alfo confined by a 

 ratchet-wheel and click to move only in the fame diredlion as the outer part A C, It is not 

 neceffary -to defcribe the operative arrangements, by which thefe two cylinders are difpofed, fo 

 as to move on the fame axis, and the ends duly applied, fo as to form one box ; while the in- 

 terior and exterior parts allowed to move independent of each other- At B is fixed a plate, 

 by which the adlionof the expanfion-pieces is communicated to the inner cylinder. A feries 

 of bars, fimilar to thofe delineated in fig. 3, are difpofed in the fpace between the two cylinders, 

 the greateft part of which they occupy, leaving only fuch an interval between A and B, as 

 may be fufficient to allow for the motion of the bars. In this interval is placed a fpring, tend- 

 ing to caufe A and B to recede from each other : and laftly, there are fide-pins proceeding from 

 the places of jundlion of every pair of bars, which refpedlivcly pafs through circular grooves in 

 the caps, and prevent the motion of the bars from being interrupted or impeded by their 

 touching either the inner or the outer cylinders. E reprefents a wheel, which is fuppofed to 

 be connefted by tooth-work, or otherwife, with the face of the external cylinder, and may be 

 confidered as the machinery intended to be moved. Or otherwife, if the clicks C and D, 

 •with the teeth they adt upon, be reverfed, and the interior cylinder be fixed to the axis itfelf, 

 that axis may be uied as the firft mover. 



• Philof. Journal, L 61. 576. 

 (Tb ht cmdudtd in our next,) 



Chemical 



