36 HOT-WATER APPARATUS. 
and completely packed in dry sawdust, or some other non-conductor, to prevent the j 
escape of heat. The reservoir may be covered with a little roof, and the space ! 
round the boiler with a sheet of lead or copper, or iron fitted round the top of the j 
furnace. The supply cistern will be under the roof, save from front, the steam valve 
put outside the roof. The supply cistern should be large enough to allow for the 
expansion of the water in heating ; about 1 gallon to every 30 in the apparatus i 
will be enough. The boiler and reservoir, being outside the pit, are accessible in 
case of necessity or any accident. 
Fig. 6. 
Fig. 6 is a section of Fig. 5, exhibiting the relative position of the boiler, reservoir, 
supply cistern, pipes, &c. It is not necessary that the foundation of the pit should 
be carried down as deep as that of the reservoir chamber and boiler; but it is 
convenient to have these deep, in order to get the pipes as low as possible, and have 
plenty of room for plants on the slate which lies over them ; the lead pipe c is 
introduced through one end of the cask, instead of being attached to its lower side : 
by being made to extend to the bottom, it acts quite as effectually, and is more 
convenient to arrange. 
Fig. 7. Fig. 3. No. 2. 
Fig. 7 is a hollow plug, which being made of cast-iron, may be employed 
advantageously to close the end of the pipes, and connect the heating with the 
conducting pipes ; and instead of the common grate, fig. 3, No. 2, it might be 
