III. PRIME MOVERS. 387 



injury by jarring, with such firmness as to give almost absolute security 

 against such injury on even very rough roads. The driving wheels are of 

 wrought iron, and are fitted with compensating motion for turning sharp 

 curves without disconnecting either wheel ; they carry about 85 per cent, of 

 the weight of the engine. The engine is steered from the foot-plate. The 

 boiler is made of best quality plates, and tested with cold water to 200 Ibs. on 

 the square inch ; the fire-box is of Lowmoor iron. 



1943. Original Model of Newcomen's Steam Engine. 



Council of King's College, London. 



1943a. The Pulsometer (Hall's patent). 



Hodgkin, Neuhaus, and Co., London. 



Self acting steam pump, a novel application of the general principle in- 

 volved in Savery's engine, A.D. 1702. The result is produced by the pres- 

 sure of the steam from the boiler upon the surface of the water in each 

 chamber of the pump alternately, without the intervention of any steam piston 

 or plunger, and the water is lifted into the chambers by a vacuum produced 

 without injection or surface condensation. The action of the steam ball 

 which governs the pulsations is purely automatic, and the moving parts, in- 

 cluding four valves, are only five in number. 



1944. Model of Captain Savery's Steam Engine. This form 

 is a modification by Dr. Desaguliers, constructed about 17 17, The 

 first complete engine of this kind was made for the Czar of 

 Russia (Peier the Great), for his garden at Petersburg. 1717 

 or 1718. Council of King's College, London. 



2137. Model of a Direct - acting Cornish Pumping 

 Engine , with cataract. 



Royal Geological Institute and Mining Academy {Director, 

 Prof. Hauchecorne\ Berlin. 



This (also with open cylinder) has a cataract of simple construction, and 

 a systematically arranged valve motion. 



The model serves, in the first place, to illustrate the general nature 

 of click-trains used as valve gear, and their application by means 

 of a plug rod and tappets worked from a beam. It also shows in par- 

 ticular the mode of employing a condenser in a single-acting engine, where 

 three valves (admission, exhaust, and equilibrium) are necessary, with their 

 three separate weigh shafts and wipers, clicks, weights, and levers. The com- 

 mencement of the expansion is shown very distinctly by the closing of the 

 admission valve. The pause at the end of the " indoor " stroke is effected by 

 means of the cataract, which is filled with petroleum ; the action of this 

 mechanism can be very distinctly observed. With a slow motion of the 

 cataract, it can also be easily noticed that the exhaust valve opens a little 

 sooner than the steam valve, in order that a sufficient vacuum may exist upon 

 one side of the piston before the steam is admitted upon the other. 



The condenser itself is omitted in order to simplify the model and to make 

 the complicated valve gear somewhat more easy to understand. A lever for 

 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. 



Bb 2 



