What is known as a 100-mesh sieve - that is, a sieve with 100 spaces to an inch - should be obtained. Any first-class hardware store can furnish the wire either from stock or on order and a home-made sieve can be constructed. A small quantity of cement should be weighed and most carefully sifted; 90 per cent of the material should pass through the sieve. By referring to statements relative to cement, under "Sand," the student will understand that extreme fineness is required in order that the cement may fit in and completely fill any voids which may exist between the particles of sand.