VARIOUS INVENTIONS. 



usual way in common engine chimneys. Of course the more 

 cold air admitted to pass through the fire, the more heat carried 

 to the top of the stack. Crenver 63-inch cylinder, double- 

 power, 8-feet stroke, with but one boiler, works five strokes 

 per minute. This gives about 1600 square feet of steam per 

 minute, and burns about 8 tons of coals in twenty-four hours. 

 The stack for this boiler is 3 feet square, and the draught rises 

 10 feet per second, and will set white paper in a flame at the 

 top of it in about a minute. Therefore, this chimney delivers 

 7200 square feet of air per minute, which is four and a half 

 times the quantity of heated air, at nearly four times the tem- 

 perature of heat that there is of steam produced from the same 

 fire, and delivered to the cylinder. 



"A blast-furnace that burns 100 tons of coal per week .is 

 blown by a 5-feet diameter air-cylinder, 4-feet stroke, ten strokes 

 per minute, double power, giving about 1600 square feet of air 

 per minute, to consume 100 tons of coal, besides giving a melt- 

 ing heat to 350 tons of ore and limestone. 



" Crenver engine has 7200 square feet of air to burn 56 tons 

 of coal per week, which is above eight times the quantity of air 

 used by air fire-places to what is used in a blast-furnace, and of 

 course must carry off a, great proportion of the heat to the top 

 of the stack, that might be saved if the engine-fire was a blast 

 instead of an air fire. 



" But suppose the idea to be carried still further, by making 

 an apparatus to condense and take 

 the whole of the heat into the cylin- 

 der instead of its passing up the 

 chimney. By having a very small 

 boiler, and a blast-cylinder to blow 

 the whole of the blast into the bottom 

 of the boiler, under a cylinder full 

 of small holes under the water, to ** 

 make the heated air give all its heat 

 to the water. 



" The furnace must be made in 

 a tight cast-iron cylinder. Both the fire-door and the hole 

 through which the blast enters must be quite tight, as the pres- 



