III. PRIME MOVERS. 453 



the injection valve only is shown, to show that this valve must be opened 

 before the engine can start. 



For simplification, the cataract which determines the short pause at the end 

 of the " outdoor " stroke is also omitted. 



2141. Model of a Horizontal Steam Engine, with re- 

 versing gear (Gooch's link). 



Royal Geological Institute and Mining Academy (Director ', 

 Prof. Hauchecortie), Berlin. 



This model is intended to illustrate the action of the link motion generally, 

 and especially that with adjustable block. 



The link can be worked in two ways. Either its centre can be suspended 

 and an eccentric rod connected with each of its ends, or its centre can be 

 fixed, and one eccentric rod only vised ; an arrangement often employed, for 

 example, in hoisting engines. 



It shows very distinctly that with two eccentric rods with their eccentrics 

 placed 180 apart, the centre of the link moves to and fro, and that this 

 error can be almost entirely prevented by giving the eccentric a little 

 advance. 



2143. Horizontal Steam Engine, with reversing gear 

 (Stephenson's link). 



Royal Geological Institute and Mining Academy (Director, 

 Prof. Ifauchecornc), Berlin. 



.With the above model this shows the two chief systems of link reversing 

 gear, their differences, and their comparative advantages and defects. The 

 link has here a different form to that employed in the last case, partly 

 simply for the sake of variety, and partly to show the influence of the position 

 of the point of suspension upon the motions of the link. 



Models of mechanisms : 



The eccentric is here also adjustable for variations of lead. 



1941. Model of Dawes' Compound Stationary Engine. 



In this the low-pressure cylinder is horizontal, and the high 

 pressure is arranged over it, at an angle of 30 to the centre line 

 of low pressure. The connecting rods couple to a single crank ; 

 the air pumps and condensers are driven off the low pressure 

 crosshead, and being two in number are arranged on each side of 

 connecting rods. Henry P. Holt, C.E. 



1937. Model of a Caloric Engine (unfinished). 



Bennet Woodcroft, F.R.S. 

 1933. Drawing of " Head's Patent Prime-mover. " 



Jeremiah Head, M.Inst.C.E. 



Being an inverted, direct-acting, non-condensing steam-engine, with steam- 

 j-acketed cylinder and covers, cylindrical slide valves, and variable expan- 

 sion gear, controlled by a liquid- cataract parabolic governor, and balanced 

 throughout for running at a high speed. 



1944a. Working Model of latest improved horizontal high- 

 pressure coupled winding engines, with winding drum as supplied 

 for coal, copper, iron, salt, and other mines. 



Messrs. Robert Daglish and Co. 



