PROCEEDINGS OF THE POLYTECHNIC ASSOCIATION. 379 



Dr. Churchill exhibited and explained the operation of the lamp-forge, 

 in which petroleum and other cheap hydrocarbons are used as fuel, it being 

 designed for light mechanical and chemical work. 



The Chairman then introduced to the audience Mr. Hamilton Towle, the 

 American engineer, who had acquired a world-wide reputation for the 

 ingenious contrivance by which he saved the steamship Great Eastern, as 

 had already been described to us at a former meeting by a passenger. 



Mr. Towle was received with hearty applause by the audience, and pro- 

 ceeded at once to describe a new invention of his for ascertaining the shape 

 of a ship's bottom while she is afloat. The principle of this machine is 

 similar to that of the conformeter for ascertaining the horizontal contour 

 of the head. A series of bars are arranged so as to slide endwise, inde- 

 pendently of each other, by means of springs; this is placed under the 

 vessel, and upon being set free, the bars move longitudinally until the end 

 of each touches the ship's bottom; at that point they are fastened by 

 catches, and upon being raised out of the water the ends of the series of 

 bars are found to describe a curve corresponding precisely with the shape 

 of the ship's bottom on the line where the bars were applied. The steam- 

 ship Great Eastern being then in Flushing bay with a hole in her bottom, 

 caused by running upon a rock, Mr. Towle took the occasion to say that it 

 would be perfectly feasible to ascertain the precise form and extent of the 

 injury done to her, by means of the apparatus just described. 



An interesting debate then followed upon the best manner of repairing 

 the great ship. 



Prof. Renwick stated that his hon was the engineer who had the direction 

 of the repairing of the ship; he had examined the plan adopted for building 

 a coffer-dam around a portion of the ship, within which the work of fasten- 

 ing on new iron plates was to be done, and he had no doubt that it would 

 be successful. 



The regular subject for discussion, " Heat and its Economical Applica- 

 tions in the Arts," was then taken up. 



Mr. Fisher opened the debate, and in the course of his remarks took 

 occasion to inquire whether it was feasible to use fuel in a liquid rather 

 than a solid form. The cheapness of petroleum was such that it might yet 

 come in competition with some kinds of coal. This kind of fuel could be 

 stowed between the skins of an iron ship like the Great Eastern, thus leav- 

 ing more room for freight. This space in the Great Eastern is, I think, 

 two feet wide; and as it extends all around the vessel, it would hold an 

 enormous quantity of oil. There would be some economy of labor in using 

 this fuel, as, instead of being transported about the deck, as coal is, it could 

 be drawn by a pump through small pipes. In regard to heating the air 

 which supports combustion, there seems to be a difference of opinion 

 among authorities. In Siemens' furnace, the air and the gaseous fuel are 

 both heated to some 1,300° before they are burned, and it, is claimed that 

 the heat is increased to the same extent. But Mr. Charles Wye Williams 

 says that there is no advantage in heating the air before it enters the fur- 

 nace. We know that when the air began to be heated some 600*^ for iron 

 furnaces, the process of making iron was accelerated. It was found that 

 one bushel of coal used to heat the blast, did more good than several 



