At the time of writing, the tanks have to deal with the sewage from a population of only 10,000 persons, as only from 15 to 20% of the connections have been made. The sewage, therefore, has been diluted with several times its volume of surplus water, and the necessary scum on the top of the sewage in the tanks has not yet assumed the usual thick matty condition observed in most systems. As there are no available means in Monterrey of having proper determinations made of the degree of purification which takes place in the passage of the sewage through the liquefying tanks, a few simple tests have been made. These tests were limited to the determination of the amount of oxygen absorbed in 4 hours, and show a purification of 50% in passing from the detritus chambers to the outlet. The sewage, although very black and full of suspended matter as it enters the tanks, leaves them in a very clarified condition. Of the total area of land acquired by the Company, 904 hectares (2,234 acres) have been leased to the Monterrey Railway, Light, and Power Company, for 99 years, the Water-Works Company reserving 5 hectares (12 acres) absolutely for future extensions of the sewage works. By giving 12 months' notice, the Company also reserves the right to utilize any part of 145 hectares (358 acres) near the tanks, should it be required at any time in the future for sewage purification purposes. QUALITY OF AND RATES FOR LABOR. All the work was practically under the direction of English-speaking superintendents and general foremen. For the ordinary skilled and low-skilled labor, Mexicans were employed exclusively, and, on the work, which was quite new to them, they proved entirely efficient and satisfactory; throughout the work, on which at some periods between 2,000 and 3,000 men were employed, chiefly under the Company's direct administration, they were very tractable and willing to do their best, and no trouble was experienced at any time. The Mexican "peon," and also the ordinary skilled workman in the north of Mexico, is intelligent, and is excellent for purely routine work, but he is not adaptable or resourceful in cases of emergency. Under intelligent and careful supervision, however, it is quite possible to get as good results as could be obtained anywhere. The daily rates of wages for a 10-hour day were approximately as given in Table 15, these rates being varied in special cases. TABLE 15.--RATES OF WAGES