Sujfplies suited to 
At some con- 
venient spot a sand 
filter 4 feet 6 inches 
square (Fig- 1) 
should be built. Its 
depth should be 
4 feet 6 inches, and 
it may be made of 
brickwork, mason- 
ry, or concrete, with 
walls and bottom 
about 14 inches 
thick, rendered in 
cement inside, and, 
if the ground be very open, it 
would be well to surround it by 
a casing of puddle about G inches 
thick. In the bottom of the filter 
must be arranged rows of bricks 
on edge, covered by a roofing of 
bricks on flat ; on this must be 
placed a layer 6 inches thick of 
coarse gravel, composed of stones 
that will pass through a ^-inch 
mesh, but not through a ^-inch ; 
then a like thickness of finer 
gravel, and finally a layer one 
foot thick of fine sharp sand sifted 
through a 1-inch mesh. All the 
filtering materials should be well 
washed, and the sand should be 
put in when the filter is full of 
water, otherwise there will be 
trouble in getting rid of the air. 
A piece of |-inch pipe should be 
fixed in one corner to make a 
way for the escape of air from 
the space under the bricks on flat. 
The reservoir should be con- 
nected to the filter by a f-inch 
galvanized pipe laid through the 
bank from the bottom of the 
reservoir, its end being protected 
by a fine strainer, and the delivery 
end in the filter fitted with a ball- 
cock. From the bottom of the 
sand-filter a f-inch galvanized 
