WATER TOWERS AND GARDEN DENS 



for working it to advantage. It is an old and well- 

 tried device, and a point in its favor not applicable 

 to other forms of supplying power, is that it can be 

 operated with any kind of fuel that is most con- 

 venient, from wood and inflammable refuse to gaso- 

 line and alcohol. This form of engine is especially 

 economical for small installations, for it not only 

 gives a choice of the cheapest fuel, but it has the ad- 

 vantage of not requiring expert and expensive at- 

 tendance. 



Mr. John F. Springer, in "Country Life in 

 America,'' says, concerning hot-air engines, "there 

 are, in one of the most prominent types, two vertical 

 cylinders in which pistons, move up and down. In the 

 one, air is compressed ; in the other, compressed air is 

 heated. The compressed air finds its way from the 

 compression cylinder into the heating cylinder 

 through a device known as a regenerator. The ef- 

 fect of heat on the compressed air is to give it great 

 expansive power. This expansion is what drives 

 the engine. The heating is done by means of a stove 

 enveloping the heating cylinder. The stove may be 

 run by kerosene, gas or anthracite coal. An idea of 

 its expense can be gained from the following esti- 

 mates of the makers : An engine able to lift three 

 hundred and fifty gallons per hour to a height of 

 fifty feet will consume twenty cubic feet of gas, two 



105 



