Tests for Fineness.

These are usually made with two sieves, one having 625 holes per square inch, the other 2,500 holes per square inch. The whole of the cement should pass through the former, and not leave a larger residue than from 8 to 10 per cent in the latter.

There is no doubt that the fineness of grinding has become the important factor in a perfect cement, but with the grinding appliances of the present day the standard cannot be raised with economy to the users, as the rate of cost appears out of proportion to the amount of improvement to be gained.