The chief sands used for ordinary building purposes in Monterrey are Nos. 10 and 11, which are procured from the bed of the Santa Catarina River. As these sands contain large proportions of lime carbonates, which make them very undesirable for important structures, their use was limited to relatively unimportant work. The best sands procurable were Nos. 5 and 9, but the long distance of the pits from Monterrey, and consequently the heavy freight rate, made their use prohibitive on economical grounds. The best of the available sands, although it was very fine, was No. 7, from Hornos, near Torreon, as it could be depended on for uniformity and could be obtained f. o. b. cars at Monterrey for 3.18[5] pesos per ton. [5] All costs given in this paper are in Mexican pesos, one peso being equivalent to 50 cents in U. S. currency. The bulk of the sand and crushed rock used was similar to Nos. 12 and 13, and reference to the cement sand tests in Table 3, will show that the manufactured sands gave very satisfactory results. Table 3 gives the average tests made with the "Hidalgo" cement and various sands, alone and in combination, for the purpose of obtaining comparative results; the mixtures tested were composed of 3 parts of sand to 1 of cement. TABLE 3.--TESTS OF "HIDALGO" CEMENT WITH VARIOUS SANDS. =====================================+============+============ Sand. | At 7 days. | At 28 days. -------------------------------------+------------+------------ Ottawa (Standard) | 305 lb. | 414 lb. Monterrey, 1-1/2 parts, } | | Hornos, 1-1/2 parts } | 188 " | 313 " Monterrey | 253 " | 365 " Hornos | 202 " | 301 " Manufactured sand, Company's crusher | 372 " | 566 " Hornos, 2 parts, } | | Crusher sand, 1 part } | 231 " | 352 " Hornos, 1-1/2 parts, } | | Crusher sand, 1-1/2 parts } | 265 " | 346 " Hornos, 1 part, } | | Crusher sand, 2 parts } | 248 " | 328 " =====================================+============+============ The Hornos sand was used during a few weeks in the latter part of 1908, when the crusher was unable to produce all that was required. Its use was restricted to thick walls which were required to be water-tight, and it was always used in equal proportions with the crusher dust. ESTANZUELA SUPPLY. [Illustration: FIG. 8.--LOCATION PLAN OF ESTANZUELA DAM.]