HEATING BY HOT WATER. 217 
for ever, while any wear, etc., is easily made good at any 
time, if not allowed to go too far and let the water in again. 
The difficulty chiefly experienced in such a work as this is 
keeping the brickwork and cement dry until the latter sets 
firmly, and this can only be accomplished by constant 
pumping (by hand, steam or wind power) from a sump-hole 
sunk just outside the stoke-hole itself, and a little deeper, 
so as to drain the latter thoroughly. 
The best way to go to work is to build the side walls first, 
using the best and perfectly sound kiln or pressed bricks, 
all wetted before use, and fresh Portland or hydraulic 
cement mortar. Now put down a good bed of concrete in 
the bottom, first, with a small drain of ordinary 2in. land- 
drain pipes, Jaid loosely, all round against the walls, 
discharging into the sump-hole, on each side. This keeps 
the floor perfectly dry, and when fairly set it may be 
covered with a course of heavy bricks on edge, well laid and 
grouted in with cement, and secondly with another course 
laid on the flat, also well bedded and grouted in. Now give 
the whole, walls and bottom, a good coat of cement and 
sand, put on very carefully, and keep on pumping until the 
whole is set quite hard. This will keep out any amount of 
water and prove almost everlasting. I have put down such 
a hole in a place where something like an underground 
river ran in a seam of gravel, and I quite thought I should 
have had to use an engine and centifrugal pump to keep the 
water down, yet it did not leak a drop, and has now stood 
for years. Remember that it is useless to try to stop an 
inward running leak with cement or anything else, as this 
cannot set. The water must be kept back until the cement 
is set, and then it will stand, if stromg enough. If at any 
