160 
Bricks. 
edileship of Varro and Murena, were cut from walls of brick ; 
and the Temple of Peace, the Pantheon, and all the Thermae, 
were composed of this material. The Babylonian bricks, which 
are in the possession of the East India company, and upon which 
Dr. Hayes has lately favoured the public with a dissertation, are 
inscribed with various figures and characters, and are supposed by 
some to be a part of that brick worl^, upon which Pliny tells us 
that the Babylonians wrote the observations which they made of 
the stars for seven hundred and twenty years. 
To the above article I would add the following remarks : 
1st. The floating bricks therein mentiond, I understand are 
made by an admixture of pumice dust with the clay. 
2d. It is worth while to try clay intended to be used as brick 
earth. If it contain coarse sand, it ought by all means to be wash- 
ed, that the small stones may subside : indeed washing and grind- 
ing clay, as the common potters do, would be a great improve- 
ment on the quality* of brick earth. 
3d. It should be tried if it contain small particles of limestone; j 
for if it do, the fire will blister and crack the brick by driving out 
the carbonic acid of the limestone. This may be done by boiling 
an ounce or two of the clay taken from separate parts of the bed, 
with a mixture of half water and half spirits of salt, or muriatic 
acid, which in an hour’s time will dissolve the limestone, and this 
can be separated or thrown down by saturating the acid with 
pearl ash. The sand can be separated from the clay, by repeated 
ablution and subsidence. 
4thly. Where bricks approaching to porcelain are wanted for j 
particular purposes, the clay should be freed from coarse particles 
by washing, and mixed with some fine sand and lime. Clay 1 
part, lime 1 part, and sand two or three parts will make a mixture 
that will enter into half fusion in a brick kiln. 
5thly. No more sand should be added to brick earth in a com- 
mon way, than is sufficient to prevent too great a contraction of 
the clay by the fire. 
6thly. Too sudden afire warps the bricks by the violent extri- 
«ation of the steam : and too violent a fire is apt to make them 
run together. Where the expence is not an object, a brick twice 
burnt, is excellent. I have already mentioned in this work, what 
I wish potters would notice, that I have never seen the coarest com- 
mon pottery that by a second gradual and continued burning, 
ii 
