36

The analyses of many cements in extensive use show quite a difference in the proportion of the lime, clay and sand; yet the best cements have a range of from fifteen to about thirty-five per cent. of silica and alumina.

This range in the proportion of the ingredients renders the making of these cements an easy task.

Is a comparatively new material which has lately been largely used in France in place of hydraulic lime. It is said to be much superior to that article for uniting stone and resisting the action of water. It is made by mixing sulphur and pulverized stoneware and glass in the following proportions:

Mix and expose to a gentle heat, and stir all thoroughly together, and then pour into suitable moulds and let it cool. It is as hard as stone at 230 degrees Fahrenheit, but at 248 degrees it melts, and may be recast or made into any desirable form by heating. Slabs of it may be joined with a paste of it heated sufficiently to melt the edges of the slabs.

West of the Pecos, adobe houses are the chief and almost the only buildings used, and this is also the custom in northern Mexico. Adobes are made of clay dried in the sun. The general form in use at El Paso, is 24 inches long, 12 inches wide and 4 inches thick. A little straw or