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ants by the insatiable demands of the killing labor, and recruits were then drawn from Puebla and other thickly populated Indian centres. Great prison barracks were built on the bare hills, and here all the criminals were sent to enter the work. The ones in charge were indifferent with regard to the lives entrusted to their care, and the slaughter, of which scant record remains in the parish burial books, and which resulted from a combination of defects in appliances for both the safety and the comfort of the workmen, was terrific. As the burial trenches were filled with new dead, the depths of the cut were tenanted by new laborers.

The victims of three years of bondage numbered fully two hundred thousand ere the work was done. Yet the results were but slight, only the excess of water from the highest lakes and streams being carried off. However, the danger from inundations of the city has been very materially decreased by the Nochistongo opening, and no more deluges have occurred since its completion.

Still the fact that the bottom of the cut was thirty feet higher than the surface of Texcoco, the lowest lying of the lakes, left the city in danger of inundation, as Lake Texcoco is constantly filling up at the rate of one and one-half inches a year and is now but a few feet below the level of the main plaza of the city.

The drainage works had long been a heavy burden upon the Mexican treasury. Up to 1637 Bancroft estimates that $3,000,000 had been expended. Up to the year 1800 the outlay had reached $6,247,670. Up to 1830 the total expenditure was $8,000,000.

Work done by the Mexican Government.-The problem which the Mexican Government had to face was very different from that which confronted Martinez in 1607. The question of preventing submergence is practically solved. The work of Martinez, unsatisfactory as it was, did a great deal to solve it. Since his day the area of the lakes has been gradually diminishing. The rapid evaporation in the rarefied air and under the direct sun of the valley partly accounts for this. Twice the water in Lake Texcoco has almost entirely disappeared, leaving only a sea of mud and a small pool. The great problem which the Mexican Government has now solved is not how to prevent an inflow of water, but how to provide an outlet for sewage. The danger to be averted was not that of drowning, but that of dying from the plague.

Lake Texcoco more than any other now menaces the security of the capital. The unwise cutting down of forests since the Spanish conquest permits the waters pouring down into the valley to bring with them annually great quantities of alluvial matter, which have so much raised the lake bottom and the water level that inundations have been of frequent occurrence. The general level of the City of Mexico is only 6.56 feet above the surface of the lake. The rainy season lasts

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MAP OF THE VALLEY OF MEXICO, SHOWING THE CANAL AND TUNNEL.

from June to October inclusive. During this season five times as much water falls as during the rest of the year, evaporation can no longer compensate for rainfall, and the valley is more or less flooded.

Originally built in the midst of a lake, the city has been left on dry ground by the receding waters. Lakes Chalco and Xochimilco have altitudes nearly four feet greater than the pavement of the capital. Still more imperiously do the lakes to the north dominate the city. San Cristobal and Xaltocan are about five feet, while Zumpango is over thirteen feet, above it.

The project now almost completed is a modification of the scheme. projected by Simon Mendez in the time of the Spanish Government, and which in 1849 was adopted by Captain Smith of the corps of American engineers which accompanied General Scott's army. The tunnel was ultimately located under the saddle and through the ravine of Acatlan, its mouth being in the Tequixquiac, near the village of that name. The works have been begun several times, and then suspended without effecting anything of importance. In 1866 the works now nearing completion were commenced. A project proposed by Señor Don Francisco de Garay, a well-known engineer of the City of Mexico, was pronounced the most feasible. But the revolutionary struggle succeeded, and for many years the work was relegated to the background.

In 1879 engineer Don Luis Espinosa, the present director of the works, took charge of the undertaking. In the first period mentioned the cutting of Tequixquiac was excavated, and the greater part of the shafts were begun; but at that point the work was stopped by political agitations.

The present gigantic work cannot have been considered to have been seriously undertaken, with a view of completion at any cost, until the year 1885, when the City Council of Mexico submitted a project to the Government to which they offered to contribute largely in the event of its being adopted.

A special commission, with ample authority to deal with the funds set aside for the work, was appointed by President Porfirio Diaz. The City Council set aside the sum of $400,000 per annum for the canal works, which sum was materially increased by the Federal Government.

In 1887 the City Council raised a loan in London of £2,400,000 to meet the cost of the work and guarantee its successful termination. The entire responsibility of the work was now assumed by the City Council, and the Government gave authority for the Council to make and collect new taxes. Still, there was not sufficient money forthcoming, so another loan was raised in London for £3,000,000, a portion of which was held for the work.

The drainage works, when carried out, will receive the surplus waters and sewage of the City of Mexico and carry them outside of the valley, and will also control the entire waters of the valley, affording an outlet, whenever found necessary, to those which might otherwise overflow fields and towns, rendering the soil stagnant and marshy. The work consists of three parts-1st, the tunnel; 2d, a canal starting from the gates of San Lázaro, and having a length of 47 kilometres, or 43 miles, its line following on the eastern side of the Guadalupe range of hills and between that range and Lake Texcoco, changing its direction after arriving at the 20th kilometre to a northeasterly one, so as to diagonally cross Lake San Cristobal, a part of Lake Xaltocan, and a part of Lake Zumpango, and arriving finally at the mouth of the tunnel near the town of Zumpango; and 3d, the sewage of the City of Mexico.

The tunnel. The contract for completing the tunnel was let to Messrs. Read & Campbell, of Mexico, but for some reason they were unable to finish the work. It was therefore continued and satisfactorily completed by the Drainage Board for a sum considerably less than the price contracted with Messrs. Read & Campbell under their superintendence as hereafter stated.

The tunnel has a length of 10,021.79 metres, or 32,869 feet (6) miles), with a curved section formed by four curves respectively of the following dimensions: The upper part has a span of 4.185 metres, or 13 feet 9 inches, and a rise of 1.570 metres, or 5 feet 1 inches; the two lateral arches have a chord each of 2.36 metres, or 7 feet 9 inches, a radius with a chord of 2.429 metres, or 8 feet, and a rise of 0.521 metre, or 1 foot 8 inches; the elevation is 4.286 metres, or 14 feet, and the greatest width is the span of the upper arch. The accompanying drawings show this section. The tunnel is lined with brick, having a thickness in the upper part of 0.45 metre, or 1 foot 6 inches, and in the lower part over which the water runs, of 0.40 metre, or I foot 4 inches in the side arches, and of 0.30 metre, or 1 foot in the radius, this latter lining being of artificial stone made of sand and Portland cement. The elevation of the invert at the beginning of the tunnel is 9.20 metres, or 30 feet 1 inches below datum; at the end of the tunnel, 17.53 metres, or 57 feet 6 inches below datum. The gradient is 0.00069 for the first 2170.74 metres, or 1 in 1500 for 7120 feet; 0.00072 for the following 5831 metres, or 1 in 1389 for 19,125 feet 6 inches; 0.001 for 4921.50 metres, or 1 in 1389 for 16,147 feet; and 0.00135, 1 in 520, for 1706 feet; these changes being in accordance with changes of details made from those of the original project, in some cases modifying the dimensions of the section. Twenty-five shafts, each 2 by 3 metres, or 16 feet 63 inches by 9 feet 10 inches, were opened at a distance of 400 metres, or 1312

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