PROCEEDINGS OF THE POLYTECHNIC ASSOCIATIOK. 513 



ill contact with the oxygen of the air let in through the upper 

 tlamper, are perfectly burnt, and thus the whole heat of complete 

 combustion is generated. 



Effect of Currents. 

 Dr. Rowell performed a simple but very interesting experiment 

 to illustrate the drawing force of currents. Two blocks of wood, 

 each an inch thick, and about one foot long, were placed on a table 

 parallel with each other and about two inches apart. Over this 

 space, and on the blocks, was placed a sheet of paper of the same 

 length. On applying a hand-bellows to one end of the passage 

 and blowing through it, many supposed the paper would be bloAvn 

 oiF. Just the opposite was the effect; the paper was drawn in 

 towards the centre of the passage. 



Patent Fuel. 



Mr. C. Edwards Lester exhibited specimens of a compound fuel, 

 and in an address of nearly an hour entertained the audience with 

 a history of the trials which had been made to produce a fuel 

 from materials which have formerly considered waste .products. 

 The fuel of which he showed samples, he said could be delivered 

 in New York at $2 per ton, and which cost at no place in the 

 United States more than $3 per ton. Peat, the basis of the fuel, 

 was found abundantly in all the States of the Union. He stated 

 that it had twice the heating property of anthracite, taking bulk 

 for bulk. It had 13| per cent greater specific gravity than anthra- 

 cite ; and while ordinary anthracite left eighteen to forty per cent 

 ash, the patent fuel never left less than three, nor more than six 

 per cent. Beside this, there is a great saving in stowage, on 

 account of the square blocks. Thus, a steamer which now carries 

 1200 tons anthracite in crossing the Atlantic, would save half the 

 space now taken up by coal, and carry in lieu thereof paying 

 goods. The importance of the new fuel on the San Francisco and 

 China route would be still greater. This fuel had been the object 

 of study for Mr. Halstead and himself during the past two and a 

 half years. They had made above 1,300 speculative trials, were 

 themselves perfectly satisfied as to its success, and were constantly 

 burning it under their small boiler (165 galls.) at Trenton, New 

 Jersey, where it started the engine in seven minutes. It had also 

 been used during a run of forty miles by steamer on the river, 



[Am. Inst.] GG 



