64 
On Water Supplies suited to 
effective horse-power per minute. If this can be obtained from 
a river or lake there is no difficulty in the matter ; but if no such 
source be available, then an injection-tank must be provided. 
The engine in the case above mentioned, doing 1 horse-power 
of water lifted, will have to give out 1'43 effective power, and 
will need 143 gallons of injection-water per hour, and therefore 
715 gallons during the five hours it is working ; this will require 
a tank about 5 feet 6 inches square, and 4 feet deep. The tem- 
perature of the water will rise about 40^, but there will be plenty 
of time for it to cool down before the water is wanted a^ain. 
The pipes connecting the tank with the engine should be sa 
arranged that the hot water should flow on to the top, and the 
cold water be taken from the bottom, by which arrangement 
the waters of different temperatures will be kept separate, and a 
supply of cold injection will be assured all the time the engine 
is running. The tank may be a pond or reservoir of any 
description, or an iron tank placed, if possible, out of doors, 
because the steam arising from the hot water may prove a 
nuisance indoors ; the water will also cool quicker in the 
open air. 
The cost of the motor is very moderate, and ranges from 
55/. for half a horse-power, to 115Z. for a three horse-power, fixed 
ready for working ; and it is an important feature in these 
engines that they are absolutely safe, because the boilers are 
practically open to the air, and the management of them may 
therefore be safely intrusted to women and totally unskilled 
persons. 
Caloric engines have been greatly improved of late, and are 
now produced in a form which renders them applicable, where 
moderate power is required. In vol. xii. of the 'Journal,' page 
596, and in vol. xiii., page 282, will be found complete descrip- 
tions of one of the most successful of these motors, that made by 
Hayward, Tyler, and Company, of London ; and in vol. xix., 
page 583, the official reporter on the implements exhibited at 
York mentions that no fewer than eight firms exhibited hot-air 
engines, and that their fuel consumption had been reduced' to an 
amount as low as 2^ lbs. per indicated horse-power per hour. 
The advantages of the hot-air engine are, that very little fuel is 
expended in getting it to work, for although the fire has to be 
lighted about half an hour before the engine will work, yet it 
will continue running some 20 minutes after the fuel is all 
consumed. It has no boiler of any kind and requires but little 
water to cool its working parts ; it therefore occupies very little 
space, is quite safe, and needs no store of water for injection. 
The disadvantage is, that the intense heat of the furnace 
acting on the dry metal of the cylinder tends to burn it out 
