HYDROLOGY OF NEW YORK 



157 



beneath is excluded and the conditions within the gage are differ- 

 ent from those existing in outside soil. This leads to the earth 

 within the gage becoming abnormally dry in times of drought, and 

 on the advent of rain absorbing more water than it would if not 

 thus isolated. In order to obviate some of these possible difti- 

 culties, new drain gages were constructed in 1888, which differ 

 from the preceding gages by being provided with an artificial 

 water table which is kept at a nearly constant hight by the addi- 

 tion of sufficient water, daily, to make up the loss by evaporation. 



An even distribution of water is insured by a layer of pebbles 

 placed at the bottom covered with another of clean sand, the lat- 

 ter reaching up far enough to cover the drain pipe. The soil 

 above, while not directly in contact with water, rests upon a satu- 

 rated layer of sand. Four drain gages were constructed on the 

 new plan — two contain a column of soil three feet in depth, ex- 

 clusive of the sand at the bottom, while the other two contain a 

 column of soil six feet in depth. One of each pair was filled with 

 soil in place in order to preserve its natural composition and 

 solidity. The other was filled with air-dried and sifted garden 

 soil. Each drain gage was made of whiteoak staves of equal 

 width, cylindrical in form and lined with sheet copper. The area 

 was one ten-thousandth of an acre as before. 



The cylinders filled with soil in place were sunk about the col- 

 umns of soil by excavating on the outside and dressing down the 

 column to fit the inside of the cylinder. The cylinder having been 

 sunk to the desired depth was inclined to one side sufficiently to 

 break the column of soil at the lower end, when the plank bottom 

 was inserted into the fissure thus formed. After various manipu- 

 lations which it is not necessary to describe, the cylinder was 

 lifted with jackscrews until it could be rolled out of the excava- 

 tion, after which it was loaded upon a wagon and hauled to the 

 pit prepared for it, where it was unloaded, with the end intended 

 to enter the soil upward. The plank ibottom was removed and six 

 inches of earth taken out to make room for the layer of sand and 

 gravel upon which the column of soil rests. The drain tube was 

 inserted, soldered to place, after which the copper bottom was 



