REI*ORT OF MR. NELSON L. DERBY.
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used principally in sheltered positions, as for court-yards covered with glass, for the portions of walls directly sheltered by cornices, etc. Hydraulic cement is best known to us at home under the names of Portland and Roman cement, and the best varieties have been supposed to come from England. At the International Exposition at Vienna, varieties have been exhibited by the Germans and Austrians, which, however, are quite equal to the best English, and are considerably cheaper. The Portland cement is prepared from a limestone with which clay and silica are mixed previous to burning. The Roman cement is obtained directly from a limestone containing the same materials naturally. The proportions are important, and upon them depend the excellence of the cement and its power of hardening under water. The variety employed, principally in Vienna, is manufactured in Kufstein, in Tyrol. United with broken stone in small pieces, beton is prepared from it, which is here applied to many uses, among others the construction of foundation walls in moist places, as an underlayer for asphalt pavement, manufacture of artificial stone, etc. The basin for a large fountain has just been completed in Vienna entirely of this substance. The foundations, commenced at a depth of some sixteen feet below the surface of the soil, were prepared of a mixture of three parts of gravel and one part of Kufsteiner cement, and upon these the bed of the basin was laid with a thickness of one foot. The parapet, after being brought roughly into form with the same material, received a coating of a mixture of one part of cement and two parts of clean sand. The mouldings were then planed out and a final coating of one part of cement and one part of fine sand was applied, planed into form and finally polished with a variety of Bohemian stone, which appears to be a soft sandstone containing mica. In conducting this work the w T hole was kept constantly moist to prevent the appearance of cracks. The workmen employed were all Italians ; and these have the reputation in Vienna of thoroughly understanding all applications of cement, and beyond this, of great faithfulness and industry. As masons in general they are unsurpassed, and doubtless, those who are now engaged in street-sweeping in New York, could be much more profitably employed in this labor. The use of cement, as mastic for buildings, is con-
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