MECHANICS AND USEFUL ARTS. 39 



the center of each flue of the boiler, to force the return of the unconsumed 

 heat, smoke, and gas, from underneath the boilers through the flues and down 

 the passage by the direct action of the exhaust steam, which exhaust com- 

 mingles with the products of combustion, becoming part and parcel, thereof, 

 aiding in the intensity of heat, round and round the continuous current, which 

 receives small supplies of fresh air in jets from a pipe arranged for this pur- 

 pose between each puff of the exhaust, which gives life to the fire, with a 

 closed chimney, furnace, and ash-pit. An additional pipe is fitted to one end 

 or middle of the drying-pipe, with a valve in it for the escape of a small por- 

 tion of the exhaust steam into the atmosphere, should it exert too much force 

 on the fire when running at the greatest speed. Conduits are provided, lead- 

 ing the products of combustion from the flues up the stack while a damper is 

 open and the fire is kindling and steam is raising, but when steam is up, the 

 damper and ash-pit closed, and the engine running, then the exhaust forces 

 all down the stack beneath the grate, and up through the fire round and 

 round, saving and burning all the heat, smoke, gas, and exhaust steam. And 

 the size of new boilers to which these improvements are to be attached, may 

 be reduced, at least one third, as the whole boiler may be enveloped hi the 

 furnace, except a small dome or drum to take dry steam from. The addi- 

 tional expense for attaching these improvements to boilers and furnaces now 

 hi use will not exceed, in general, five dollars to the horse power, and hi the 

 construction of new engines and boilers, the cost will actually be less than 

 the ordinary boilers and furnaces now in use. 



Ericsson's Hot- Air Engine. During the past year reports have been from 

 time to time circulated that the caloric engine, devised by Mr. Ericsson, had 

 proved a complete failure, and that the principle on which it was constructed 

 had been finally abandoned by Captain Ericsson, who had substituted steam 

 engines in the ship with which his experiments were made. These reports 

 awakened profound regret, not only hi the minds of those who were aware 

 from personal knowledge of the great abilities, unwearied labor, and large 

 sums of money which had been devoted to this experiment, but also on the 

 part of the public, which had become deeply interested in its success. Nor 

 was it easy to understand, in the face of results known because seen to 'have 

 been attained, how the principle of the caloric engine could have proved a 

 failure : for in the trip of the Ericsson to "Washington a propelling power was 

 certainly obtained at less expense for fuel, and with a greater saving of room, 

 than had ever before been achieved. 



From the following letter, communicated to the New York Times by Captain 

 Ericsson, it will be seen that he has not abandoned the caloric engine that 

 while mechanical difficulties have prevented the satisfactory application of the 

 principle, his faith in the principle itself remains unshaken, and that he is still 

 engaged, with unwearied assiduity and with unflinching courage, in the pros- 

 ecution of experiments for its perfection. He says: "The assertions of my 

 opponents that the caloric engine has failed and been abandoned, and that a 

 ' new steam engine' has been put into the Ericsson, are all wholly unfounded. 

 Every trial made has proved the soundness of the principle of the caloric en- 

 gine, an extraordinary saving of fuel being hi every instance well established. 



