Portland Cement.

Progress, 1 October 1908, Page 421

Portland Cement.

Portland cement is unquestionably the best cement for external plastering if mixed in the proper proportions, and the work prepared to receive it. The walls should be roughed, to form a key for the cement, then well brushed down and wetted The cement, composed of Portland cement, one part, clean, sharp sand, two parts, should be laid on three-quarters of an inch thick When the moisture is going off it should be scored, so as to form a key for the floating The floating coat should be a quarter of an inch thick, composed of equal parts of Portland cement and washed sand, trowelled to a smooth, even face. Concrete lintels are composed of one part Portland cement to four parts coke breeze. Window heads, sills, slabs of concrete, are composed of Portland cement and sand, or granite chippings, slag, crushed stone, brick, etc. The concrete is composed of one part Portland cement to three parts of sand or

granite, the whole well incorporated in a dry state, and then mixed with water and cast in moulds to the required shape. Further, artificial stone and paving slabs, to withstand wear and tear and atmospheric influences, etc., are satisfactorily produced by a composition of one part Portland cement, two parts fibre asbestos (perished), one part crushed brick, to six parts of water, thoroughly incorporated in a mill, the slurry being run out into moulds of the size and shape required, pressure applied and then allowed to dry. The aggregates m some cases require crushing and grinding, it being a point of the utmost importance that the pieces of the various

materials should be angular, and not round Any local brand of Portland cement of the standard quality and strength is suitable, or such brands as "Saxon," "Peters," etc., will be found efficient. Cracks in such work are caused by inferior materials, workmanship, insufficient mixing, the work drying too quick, the laying of the cement on walls of too much suction for water, laying one coat on another before the lower one has properly set, or by the use of too little or much sand; lastly, the materials being spread out to cool, otherwise, if used hot, the concrete or cement work will blow after setting, causing cracks to appear on the surface — Charles A. Longley.

The a\erage height of the elephant is 9ft. A single tobacco plant will produce 360,000 seeds.