402 Description of a Rolaiive Steam Engine. 



circle be fitted as shall form a complete circle, exccpting^ 

 the space LL, which is occupied by adjusting screws, or 

 springs to keep the segments close together. The segments 

 are the breadth (or nearly) of the groove CD, and of a 

 depth less than the depth of the groove C D. Those sides 

 cf them which apply to each other are to be ground to- 

 gether plain, and air-tight if possiblfe. Their under sur- 

 faces, which arc shown in fig. 1., arc to be il at, so that 

 the whole may form one con)plelc plain surface, excepting 

 the sj«ce before mentioned, which is taken up by adjust- 

 ing screws or springs LL, which screws or springs are 

 placed so far below tlie surface as to let a roller pass by 

 them, which will be mentioned hereafter. 



Figs. 2 and 5 represent vertical sections of the plate and 

 grooves of fig. 1, resting upon a circular chamber or hol- 

 low space Y Y, to which ch-'imbcr the said plale forms a 

 hsht covering, excepting that space occupied by the springs 

 or screws LL as before mentioned. 



I, the centre of all the grooves and circles before described, 

 is also the centre of the shaft. On the shaft 1 is fastened 

 a plate or coupling ZZ, in which is inserted a bar F. This 

 bar may be of any given breadth, but in depth must be less 

 than the depth to which the circle EP> was cut down below 

 the surface A B. To this b::r is attached a wheel or roller 

 G, shown in fig. 3 upon a larger scale. The manner in 

 which it is attached to the bar F is also there seen, and it 

 is so attached to it that the top of the wheel or roller G 

 shall always be higher than the top of the bar F. The 

 wheel G being attached to the bar F will, when the 

 bar is made to revolve, describe a circular path H H H 

 along the plain surface of the segments before described. 

 Let that portion of the plain surface of each segment which 

 answers to the path of the roller G be rounded off, in such 

 a manner as to make \hat portion of the surface an arc of a 

 circle, the convex circumicrcnce of which is presented to 

 the roller G. In fig. 3, at tl is shown a pet;pendicular 

 view of one of tlie segments, rounded off in the manner 

 described, and presenting its convex circumfcrciice to the 

 roller G. There may likewise be another roller attached 

 to the bar behind it, to lower down the segments in the 

 saiTie manner in which they are raised by the first roller. 

 Now it is obvious, all the saiil segments biing in their 

 places in the groove CD fig. 1, that the roller G, in per- 

 iorming a revolution round the centrc'I, must travel along 

 a scries of couvtx arcs of circles C(]ual in number to the 

 number of segments iu the groove C D. The groove D E 



is 



