62 ANNUAL OP SCIENTIFIC DISCOVERY. 



propelled by engines of this kind; one of which is to be 1,500 tons 

 burthen, and the engines are to be of 150 horse power. Mr. Rennie 

 said that arrangements are made for dispelling the ether vapor that 

 escapes, so that there is no danger of its ignition. Mr. Sykes Ward 

 observed that good ether does not corrode iron ; therefore no objec- 

 tion to its employment could arise from that cause. Mr. Fairbairn 

 said that 2| Ib. of coal per horse power are consumed in the best Lan- 

 cashire engines, worked expansively, whilst the steam-boats on the 

 Humber burn about 10 Ib. of coal per horse power ; and as it appeared 

 from Mr. Rennie's report of the working of the combined steam and 

 ether engine that the duty was greater than that of the best Lanca- 

 shire steam-engines, the advantage of the combined action compared 

 with that of the marine engines on the Humber was very important. 



ERICSSON'S ENGINES. 



The Scientific American states that the folio wing alterations and im- 

 provements have been made in the Ericsson engines, since the last trip 

 of the vessel. Immediately above the fire is placed six layers of cast- 

 iron pipes, nine feet in length and three and a half inches in diameter ; 

 above these pipes are two heaters, 9 feet in length, and 2 feet 5 inches 

 in diameter. These heaters are filled with tubes 2 inches in diameter, 

 through which pass the flame and smoke from the fires. The cylinder 

 is 5 feet 2 inches bore, and about 7 feet stroke. He also employs a 

 cooler 10 feet in length, and 3 feet in diameter, filled with tubes H 

 inches in diameter ; among these tubes circulates a supply of cold 

 water for the purpose of condensing the air after it has passed from 

 the cylinder. These various parts communicate with each other, but 

 not with the external air - - the cold air from the cooler passing in the 

 heaters, then through the cast-iron pipes immediately over the fire, 

 then into the cylinder and back to the cooler again. 



A late number of Silliman's Journal contains an investigation of 

 Ericsson's Caloric Engine, by Prof. Norton. The conclusions of the 

 author are thus summed up : 



1. That Ericsson's Hot Air Engine, as compared with the condens- 

 ing marine steam engine, in its most economical operation, has shown 

 the ability to do the same work with the use of from one-sixth to one- 

 third less fuel ; and, that if its full estimated power should hereafter 

 be developed, the saving effected would be 70 per cent. 



2. That for the same actual power, its weight is about three times 

 as great as that of the marine steam engine, and that in case its esti- 

 mated power should be obtained, its weight would be as much as 

 thirty per cent, greater. 



3 That in respect to the space occupied with the engines and coal, 

 the advantage is decidedly in favor of the steam engine. 



4. That the great weight of the engine, in proportion to the power 

 developed, must prevent, for the present, the realization of a high 

 speed in the propulsion of vessels. At the same time it is to be 

 admitted that the full estimated power is adequate to the production 



