

A/A' WILLIAM SIEMENS, F.R.S. 357 



accompanied by the emission of any^such products. The plun 

 o'M-isted simply in filling the fire-box with u clamp of bricks so 

 arranged that between the masses of brick innumerable channels 

 provided through which air might circulate and rob the 

 brickwork of its heat in order to communicate it to the boiler. It 

 miirht appear, at first sight, that the quantity of brickwork re- 

 quired for such a purpose would be enormous, but a little consider- 

 ation would show that was not the case. Firebrick had a heat 

 capacity about equal to that of water of the same volume ; there- 

 fore if a cubic foot of brickwork was heated 1 that heat would 

 sutlice to heat a cubic foot of water 1. But the brick had the 

 advantage of being susceptible of being heated 1,000 above the 

 standard which it must retain to evaporate a cubic foot of water. 

 The question was, how many cubic feet of water were required to 

 be evaporated, in passing from Dover to Calais. Taking as the 

 rate of evaporation 5 cubic feet per mile, and taking the length of 

 the tunnel as 30 miles, that would give a total evaporation of 

 150 cubic feet of water, and the brickwork necessary to yield that 

 amount of heat would be 150 or 160 cubic feet, which would 

 weigh about 17 tons, constituting a mass 6 feet by 6 feet by 

 10 feet, if one-half of it was allowed for air spaces. He proposed 

 to heat the brickwork at the station in a furnace, and to lift it 

 bodily, being clamped with iron, into the fire-box of the engine, 

 where it would be fixed by bolts. Currents of air would be directed 

 through it at the place of the ordinary fire-door, which, passing 

 through the tubes of the boiler, would produce steam. At the 

 end of the journey the engine would go over an empty pit, where 

 the mass of brickwork would be lowered by an hydraulic ram, to 

 be heated again for another journey. The boiler would, at the 

 same time, be filled with water at 300 Fahr., so that evaporation 

 would at once commence under the most favourable conditions. 

 If the proposed scheme of the Channel Tunnel were ever carried 

 out, he thought this plan ought to be fully considered, because he 

 saw no difficulty in carrying a store of heat sufficient to take a 

 locomotive engine from Dover to Calais, whereby mechanical ven- 

 tilation would be saved and a wholesome atmosphere insured in the 

 tunnel. 



