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 186 CEMENTS sand, and exposed for several weeks to the action of the air. This has also been used with good results in the harbors of Marseilles and Toulon, and at various other places, in both fresh and salt water. The piers enclosing the harbor at the ocean terminus of the North sea canal of Holland are laid in Portland cement, and the same material enters into the struc- ture of the Cherbourg breakwater. The foundations of Fort Tompkins and Fort Rich- mond in New York harbor are composed of concrete made of hydraulic cement, sand, and fragments of granite, hi the proportion of one part of cement to three of sand and five of granite. Exterior stucco work is now to a great extent made of hydraulic mortar. For further information in regard to the details of the technical manipulation employed in man- ufacturing, using, and testing hydraulic, ce- ments and mortars, see " Practical Treatise on Calcareous Mortars and Cements," by L. J. Vicat (London, 1837) ; " Observations on Cal- careous Cements," &c., by Major Gen. Sir 0. W. Pasley, K. C. B. (London, 1847) ; Henry Reid's treatises on Portland cement and on concrete (London, 1868 and 1869) ; the prac- tical essay of A. Lipowitz on Portland cement (translated by W. F. Reid, London, 1868) ; the work of Dr. W. Michaelis, Die hydraulischen Mortel (Leipsic, 1869) ; Gen. Q. A. Gillmore's treatise on "Lime, Hydraulic Cements, and Mortars" (New York, 1872); and "Report on the Hydraulic Lime of Teil," by Leonard F. Beckwith, 0. E. (New York, 1873). The fol- lowing table of the composition of ancient mor- tars, with the names of the analysts, is taken from Mr. Reid's treatise on concrete, and will be found interesting to peruse in connection with the various theories of the hardening of mortars : Ij CONSTITUENTS. Carbonate of lime. . I 9'47 of magnesia 0*69 Silicic acid 5-80 Alumina 2-41 HydraM sulph. lime 1-50 Oxide of iron 80-25 Lime Magnesia Potash Soda Carbonic acid. . . Sulphuric acid. . Silicic acid and fine sand Organic matter. Coarse sand Small atoms Water s 9-80 0-79 4-80 8-00 BHO 0-21 is. 2-16 0-99 26-40 0-97 -.5 II Ij Jhl 0-40 51-58 0-70 40-60 0-82 0-96 0-24 8-09 Total '99-52 100-99 100-2 ' 98-89 99-68 I 98-40 98-78101-86 2-64 0-92 45-70 1-00 0-82 49-65 1-09 1-04 8-90 8-07 51 14-70 4-92 15-80 0-80 1-01 2-12 11-80 41-10 2-28 6-20 2-82 29-88 0-25 8-40 8-49 1-60 'i-'oo l 16-31* 4-28 18-71 0-71 18-61 8-20 fj ill 10-W 8-67 25-19 0-90 17-97 80-24 2-48 6-60 96-59 -.2 t-"i ii aJ $=2 g = 1 111 The mastics and other oily cements of Lon- don have nearly gone out of use on account of their want of durability. They were com- pounds of lime, sand, litharge, and linseed oil. Gypsum and gypseous cements are much used for internal plastering and decoration. The rapidity with which plaster of Paris sets when mixed with water makes it an article of great value. The gypseous cements mostly used in England are Keene's and the Parian. The former is obtained by recalcining plaster of Paris which has been slaked with a saturated solution of alum and water, and again slaking it with a saturated solution of borax. Bitu- minous cements are employed as substitutes for flagging in paving streets, and to protect the extrados of arches from the effects of water ; and for this they have much utility, because in all new masonry there are movements which fissure the coatings made in hydraulic cements, so that it is almost impossible to render them impermeable to water, and the elasticity of bituminous cements is well calculated to over- come the defects of the more unyielding stony compounds and render them particularly ser- viceable in making repairs. They are made from natural asphaltnm, which is mixed with chalk or carbonate of lime, or with hydraulic cement. A cement which is made in Silesia for covering roofs is composed of Portland cement, coal or wood tar, and a small portion of sulphur. Among the resinous cements are Varley's, which is made by drying by means of a red heat 16 parts of pulverized whiting, and when cold stirring it in a melted mixture of 1 6 parts of black resin and one of beeswax. Singer's electrical and philosophical apparatus cement consists of 5 Ibs. of resin, 1 Ib. each of beeswax and red ochre, and two tablespoonfuls of plaster of Paris, melted together. The ochre and plaster should be previously calcined, and ad4ed after the other ingredients are melted. Lapidaries' cement for holding gems while they are being cut is made of resin and red ochre or
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