400 
Brick -Making. 
Verf best hard sound bricks, be the colour of them what 
they aiay, and be the cost what it will. Such bricks are 
easii . known by their sound, and by their striking fire 
with steel. It will be found that, besides the comfort 
and firmness of the building, they will be cheaper than 
placr; bricks, together with the expense of battening tiie 
Wails. 
In the interior of the country tiles are almost uniformly 
tor roofs of houses, and in some instances on barns ; 
but between Dorking and Horsham a heavy but very du- 
rable sort of slate stone is used. Nearer London either 
Welch or Westmoreland prevail As there are many 
persons who give the preference to tiles, it may not be 
amiss to know the result of a curious experiment on that 
subject as related by the Bishop of Llandafl 
That sort of slate, other circumstances being the 
same, is esteemed the best which imbibes the least water ; 
for the imbibed water not only increases the weight of the 
covering, but in frosty weather, being converted into ice 
it swells and shivers the slate. This effect of frost is very 
sensible in tiled houses, but it is scarcely felt in slated 
ones ; for good slate imbibes but little water ; and when 
tiles are well glazed they are rendered, in some measure, 
with respect to this point, similar to slate. I took apiece 
of Westmoreland slate, and a piece of common tile, and 
weighed each of them carefully ; the surface of each was 
ab^ut thirty square inches ; both the pieces were immers= 
ed in water for ten minutes, and then taken out and weigh‘d 
ed as soon as they had ceased to drip ; the tile had imbib- 
ed above a seventh part of its weight of water ; and the 
slate had not imbibed a two-hundredth part of its weight i 
indeed the wetting of the slate was merely superficial. 
I placed both the wet pieces before the fire ; in a quar^r 
of an hour the slate was become quite dry, and of the 
same weight it had before it was put into the water ; but 
the tile had lost only about twelve grains of the water it 
