944 REPORT OF COMMISSIONER OF FISH AND FISHERIES. 



eugiue of Coimt du Trembley would have contimied ruuning had there 

 uot been immense difficulty and peril iu usiug- ether in reciprocating- en- 

 gines and pumps. 



It occurred to me to introduce a form of condenser and refrigerator 

 consistiug of tubes within tubes, as described further on, which reduced 

 the volume of ether, distributed over a wide surface within a narrow 

 compass, and enabled me to construct an aj^paratus of great solidity and 

 safety. At the same time, one inconvenience attending the ether-ma- 

 chines was that the brine used, common salt and water, was apt to freeze 

 up in the refrigerator-tubes and burst them. This I overcame by the 

 use of an aqueous solution of glycerine, and later on I have economized 

 by using chlorine of magnesium and water, with some glycerine added, 

 according to the temperature at which it is proposed to work. 



Without attempting a detailed history of improvements suggested 

 from time to time, my main object for years was to overcome the then in- 

 evitable use of a reciprocating-pump in which liquefiable gases were alter- 

 nately liquefied and volatilized, to the detriment of efficiency. This was 

 found one of the most objectionable features in the use of sulphurous 

 acid and ammonia, inasmuch as a film of liquid remains after every 

 stroke between the piston and the cylinder-cover, and expands on the 

 return stroke so as to interfere with the suction of a fi'esh charge. 



I must enlarge somewhat on this subject of 



E.-ENGII^ES AND PUMPS. 



In all freezing-machines, except those depending on absorption of a 

 gas by water and its distillation, it has been a matter of primary impor- 

 tance to secure an economical engine, and a pump capable of producing 

 a vacuum, or compressing a liquefiable gas. 



AU kinds of engines have been used — upright and horizontal high- 

 pressure and compound engines. The inevitable waste, attending the 

 production of steam, and its imperfect utilization, in the best form of 

 reciprocating engines, have been regarded as really incurable evils, in 

 the production of artificial ice by means of pump-machines. 



The method of transmitting power has necessarily attracted consider- 

 able attention, and in one machine the crank- shaft has been the seat of 

 all strain, whereas in other cases, with an engine placed on a bed-plate 

 on a line with the pump, the pressure on the engine-piston was greatest 

 when there was least resistance, and vice versa. 



But the difficulties of the engines, common to all machines using steam, 

 api)eared of less importance than the imperfections of the reciprocating 

 pump. Whether single or double acting, the change in the direction of 

 motion at every stroke, the universal clearance or imperfect discharge 

 of the gas from the pump at each revolution ; the cumbersome and noisy 

 valves, which are frequently broken by striking ; the leaky stuffing-boxes, 

 and the ample surface of the x^iston-rod, for exposing a layer of gas to 

 atmospheric contact, as many times per minute as the piston runs its 



