that the sugar proved positively detrimental to the cement, while it
increased the tenacity of briquettes of lime.

Stone which will pass a 2 inch is usually specified for ordinary
concrete. It will be found that stone broken to this limit of size has
fifty per cent. of its bulk voids. This space must be filled by mortar
or preferably by gravel and mortar. If the mixing of concrete is
perfect, the proportion of stone, by bulk, to other materials should
be two to one. A percentage excess of other materials is, however,
usually allowed to compensate for imperfection in mixing. While an
excess of good mortar is not detrimental to concrete (as it will
harden in course of time to equal the stone), still on the score of
economy it is advisable to use gravel or a finer grade of stone in
addition to the 2 inch ring stone to fill the interstices--gravel is
cheaper than cement. The statement that excess in stone will give body
to concrete is a fallacy hardly worth contradicting. In short, the
proportion of material should be so graded that each particle of sand
should have its jacket of cement, necessitating the cement being finer
than the sand (this forms the mortar); then each pebble and stone
should have its jacket of mortar. The smaller the interstices between
the gravel and stones, the better. The quantity of water necessary to
make good concrete is a sorely debated question. The quantity
necessary depends on various considerations, and will probably be
different for what appears to be the same proportion of materials. It
is a well known fact that brick mortar is made very soft, and bricks
are often wet before being laid, while a very hard stone is usually
set with very stiff mortar. So in concrete the amount of water
necessarily depends, to a great extent, on the porosity or dryness of
the stone and other material used. But as to using a larger or smaller
quantity of water with given materials, as a matter of observation it