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EXPOSITION AT VIENNA.
ducted under similar conditions to those described. The exact proportion of sand to be added to the cement cannot be fixed for all varieties, but is always dependent on the quality of the latter. In some cases in Vienna I have understood that the cement is applied without intermixture of sand at all. It must be worked into form immediately upon application, which must ensue directly upon mixing with water. The latter must be used unsparingly, and the whole kept thoroughly wet for several days to prevent the appearance of cracks. It is not, as the ordinary lime mastic, applied in three layers, but all at once, the other conditions being, however, the same as those described in connection with that substance.
The best varieties of cement for mastic are those which set slowly, but the proportions vary for different climates, and can be best determined by experiment. In Vienna the Kufsteiner cement costs about 75 cents per hundred-weight and the labor of application as mastic varies from 30 cents to 75 cents per square yard, according to the nature of the work. Many of the more elaborately ornamental features of fronts, which cannot be directly prepared by the workmen with his ordinary tools, or which require a certain amount of artistic skill, such as consoles or brackets, ke 3 r -stones, fretwork, etc., are cast in cement and afterwards attached in position with irons, and, if hollow, filled with cement. These, of course, have no weight to support, but are purely decorative. Better and more durable than cement for such purposes is terra-cotta, which is now widely used in Vienna, and is only prevented from supplanting the cement castings by its greater cost. The color of these mastic fronts is that of light sandstone, and is very pleasing to the eye; only when a deposit of saltpetre appears from the brick wall beneath is it customary to paint them. Very pleasing decoration of Smooth surfaces of mastic is also produced by the Italian art of Sgrafitto painting. The finest modern specimens of this are to be seen in the passage Victor Emanuel, in Milan. The process is the following: With the mastic is mixed hard coal and charcoal dust, also Frankfort .black, previous to its application. After setting it receives a thin coating of slack lime and water, which while still moist is scraped away by a pointed steel instrument, in such a manner