Bricks. 161 
might not be converted into stone ware . I have done this repeat- 
edly. 
7thly. If the bricks are required to be glazed externally, it 
can be best done by throwing a bushel of common salt into a kiln 
of bricks while at their greatest heat, and stopping the top of the 
kiln. 
8thiy. The best bricks are made of well burnt clay containing 
but a small proportion of fine sand. Turning up the earth in 
the autumn, to expose it to the winter’s frost— -well working it in 
the spring before it is moulded — gradual and continued burning 
in the kiln or clamp, are all of them absolutely essential to a good 
brick : few of these requisites are usually well performed. 
The legislature in England has often interfered in the manu- 
facture of bricks ; and considering how much the health of the 
inhabitants of large towns, depends upon the goodness of bricks, 
especially in such a climate as England, I am not much inclined 
to find fault with this interference. By 12 Geo. 1. ch. 35. earth 
or clay designed for bricks made for sale, shall be dug and turn- 
ed once at least between the first day of November and the first 
of February ; and not made into bricks till after the first day of 
March : nor shall any brick be made for sale, but between the 
first day of March and the 29th of September. But the 10 Geo. 
3. ch. 49. earth may be dug at any time of the year, provided such 
earth be turned once before it be made into brick. By stat. 3 0 
Geo. 2. ch. 22. not more than 720 bushel of sea coal ashes screen- 
ed through a half-inch screen, shall be mixed With the earth of 
100,000 bricks. By 17 Geo. 3. ch. 42. all bricks made for sale 
shall, when burned, be not less than 8| inches long, 2|- inches 
thick and 4 inches wide. 
From the want of breeze, or the small cinders of sea coal 
ashes, more fuel and longer time, are required to burn bricks 
in this country than in England. The clamps near Philadelphia 
usually contain about 50,000 bushels ; 40 by 40, and 32 high; half 
a cord of wood is allowed to 1000 bricks ; the burning of a clamp 
takes about a week. Near London, the clamps usually contain 
100,000, and the burning last about a fortnight. 
9thly. I weighed two bricks that had long been kept in a 
room in the college here and were perfectly dry. They weigh- 
ed lOf lb. Immersed in water for an hour they weighed 1 J ib. 
T. C. 
VoL. Ill, 
X 
