30 ANNUAL OF SCIENTIFIC DISCOVERY. 



no serious accidcMit from earth, gas, or water, occurred iu the 

 ■whole conrso of the work. 



Tlie soil has Ix'cn foiuitl to be so uniform tliat only one leakage 

 of water tiuough the tunnel ever occurred, and that only distil- 

 ling througii a crevice at the rate of a bucketful in five minutes. 

 This occurred in Sojitembcr, 1.^05. Tlie workmen left in dismay, 

 but soon returned and r('j)aired the crevice. From tliat lime no 

 accidents of any importance have occurred to hinder the progress 

 of the work, witli the exception of one or two slight escajies of gas, 

 which resulted in notiiing serious. Several stones, varying from 

 the size of an i^'^'^ npwanls, have been met with, l)ut very few in 

 comparison with the great mass of clay. The only fault to be 

 found with the clay was, that it contained too much calcareous 

 matter U> make good bricks. The contractors claim that they 

 have lost numey on this account. The bricks formed of the clay 

 found iu the tunnel would not burn solidly, so that they were 

 obliged to get Ijricks elsewhere. 



The lining (if the shore-shaft consists of twelve inches of the best 

 brick and cement, in three shells; about 4,000,000 bricks were 

 used in its construction. 



On the IGth oH November, 18G6, the opposite gangs of work- 

 men were within two feet of each other, and this ])artition was 

 broke tinough on tiie following day in a formal manner by the 

 IJoard of Tublie Works. The accuracy of the measurements of 

 the engineer was such, that the two lines of excavation coincided 

 iu the centre within nine and one-half inches, and the lloors joined 

 with a dilVerence of only one inch. 



Water is to be let into the lake-shaft by three gates, on differ- 

 ent sides, and at dilYerent heights. The lowest is five feet from the 

 bottom of the lake ; the next ten feet, and the highest fifteen feet. 

 Flumes through the surrounding masonry, also closed by gates 

 and gratings at their outward ends, will conduct the water to the 

 shaft gates. All the gates can, of course, be opened and closed 

 at pleasure. ^ 



The tunnel, as now constructed, will deliver, under a head of 

 two feet, 19,U00,OU0 gallons of water daily ; under a head of eight 

 feet, 38,000,000 gallons daily, and under a head of eighteen feet, 

 57,000,000 gallons daily. The velocities for the above quantities 

 will be one and four-tenths miles per hour, head being two feet ; 

 head being eight feet, the velocity will be two and three-tenths 

 miles per hour; and the head being eighteen feet, the velocity will 

 be four and two-tenths miles per hour. By these means it will be 

 competent to supply one million iieo2)le with lifty-seven gallons 

 each per day, Avith a head of eighteen feet. With regard to the 

 character of the work, the material met witli in the jirocess of 

 excavation has been stiff blue clay throughout, so that the antici- 

 pations of the contractors have, in this respect, been fulfilled. 



The crib, since it was sunk and loaded, has been thoroughly 

 tested by violent storms, and, during the winter, by the moving 

 fields of ice. It withstood the shocks, both of the ice and the 

 storms, without injury, and the least movement of it, since it was 

 fairly loaded, has not been discovered. 



