946 REPORT OF COMMISSIONER OF FISH AND FISHERIES. 



lar flat piece of metal screwed to tlie rectangular block, and which, on re- 

 moval, is found to close the space in which a slide moves vertically. The 

 removal of four screws from the circular cover exposes the end of the 

 piston, wich is arranged eccentrically to the shaft. The inner covers at 

 either end i^ractically complete the piston, but their main function is to 

 equalize the wearing surface, and effectually to i)revent leakage. 



This is a vital point, and it is necessary to understand that one cause 

 of serious imperfection, in most rotary engines and luimps, has been the 

 unequal wear at the ends of eccentric i^istons, which naturally travelled 

 farther at their peripheries than at their centres. Once the inner covers 

 are bolted to the piston this detrimental condition is obviated. 



At the greatest distance from the shaft a slot is cut into the iiiston 

 and into this is fitted a steel bar, packed automatically against the cylin- 

 der through a channel communicating with the pressure-side of the steam 

 or gas. 



In the vertical slot above the piston is a broad slide of equal length 

 with piston and cylinder. It divides the whole into two chambers 

 and rides on the eccentric piston. Its lower edge is convex and its 

 upper surface is perforated by two ports which lead through to the press- 

 ure-side of either engine or pump. 



The slide fits snugly in its socket and its weight exerts some influence 

 to maintain it in contact with the piston. Corresponding to the upper 

 orifices in the slide are the valve-openings for the inlet or exit, as the 

 case may be, in the engine and pump. Immediately on the low-pressure 

 side of the slide, midway in the length of the cylinder, is the induction- 

 port provided in the pump with a valve to prevent recoil of gas. 



Tig. 1. 



The first or lateral view appropriately indicates the compact and solid 

 aspect of this apparatus, and indicates the manner in which the cylinder 

 is fixed to the bed-plates, the nature and i^osition of the outer covers 

 with their stuffing-boxes. 



