PKOCEEDINGS OF THE POLYTECHNIC ASSOCIATION, 569 



Mr. Pell asked if any gentleman present could state whether 

 iron contained electricity all through it, or only on the surface ? 

 He thought that all iron contained electricity to repletion. 



Mr. Hedrick said that the wire was affected with electricity 

 through the whole surface, with the exception that one end con- 

 tained the negative and the other the positive electricity. 



Dr. Knight. — Some few years ago some experiments had been 

 made, and it was found that the iron was given polarity through- 

 out it. He thought that electricity was to be found all through 

 the wire, and not on the surface only, 



Mr. Garvey said that percussion on a bar of iron would crys- 

 talize it. One phase of the vibration will be positive electricity 

 and the other negative. 



FUEL. 



Mr. Hedrick. — The fuel question is a very large and a very 

 material one. As a material question, it is hardly second to any 

 that we will come across. The primitive fuel was wood, and all 

 other fuel that has been used up to the present time has been 

 similar. Carbon is the main thing in the wood. What we call 

 charcoal is carbon. Fuel is merely heat stored up, and when 

 burning it we are only bringing it out. You may say that the 

 coal is the fuel and the oxygen the supporter of combustion, or 

 that the oxygen is the fuel and the coal the supporter of the com- 

 bustion. Either is correct. The fact is, that for every pound 

 of oxygen that enters into the fuel, it will raise twenty-nine 

 pounds of water from 32 deg. to 212 deg., making a difference of 

 180 deg. No fuel is pure. Wood is not pure. The earthy mat- 

 ter which all fuel contains is incombustible, and takes away from 

 the heat, because it has to be heated up. For making steam, one 

 fuel is as good as another, if it contains as much combustible. 

 In this country the question of fuel for ships was considered by 

 Walter R. Johnson. When we burn hydrogen in oxygen, water 

 is the product. You can produce a very high heat by the oxo- 

 hydrogen blowpipe. Pure carbon and pure oxygen make the 

 the best heat. Air contains, besides oxygen, four-fifths of nitro- 

 gen. In the making of steam we can always get the whole of the 

 heat. The cheapest mode of warming is by steam. If you reduce 

 wood to powder, you cannot burn it. You cannot burn lamp- 

 black, and it is only fine charcoal. The reason is, that the quan- 

 tity of combustible heat at one part is so small that it cannot 



