DRAINING AND WASHING WET MARL PITS. 289 



quite wet and soft by the water oozing through it. With gravel 

 shovels, this was easily cut under from one to two feet along the 

 whole length of the old pit, and, as fast as was desirable, the upper 

 earth, thus undermined, fell into the old pit ; and afterwards, when 

 that did not take place of itself, the fallen earth was easily thrown 

 there by shovels. As the earth fell separated into small but com- 

 pact masses, it was not much affected by the water, even when it 

 remained through the night before being shoveled away. No dig- 

 ging was required, except this continued shoveling out of the 

 lowest sand stratum ; and whether clay, or stones, or roots, were 

 mixed with the falling earth, they were easy to throw off. The 

 numerous roots, which were so troublesome in the former operation, 

 were now an advantage ; as they supported the earth sufficiently to 

 let it fall only gradually and safely ; and before the roots fell, they 

 were almost clear of earth. The whole body of earth, notwith- 

 standing all its difficulties, was moved off as easily as the dryest 

 and softest could have been by digging altogether. The thicker 

 the overlying earth, the greater is the facility of undermining, and 

 causing it to fall by its own weight. 



In working a pit of low-lying and wet marl, covered and sur- 

 rounded by higher ground (class III.), no pains should be spared to 

 drain it as effectually as possible. Very few beds of marl are 

 penetrated by veins of running water which would deserve the 

 name of springs ; but water generally oozes very slowly through 

 every part of wet marl, and many small springs often burst out 

 immediately over its surface. After the form of the pit and situa- 

 tion of the road are determined, a ditch to receive and draw off all 

 the water should be commenced lower down the valley, as deep 

 as the bottom of the area where the carts are to stand is expected 

 to be made ; and the ditch opened up to the work, deepening as it 

 extends, so as to keep the bottom of the ditch on as low a level as 

 the bottom of the area. It may be cheaper, and will serve as well, 

 to deepen this ditch as the deepening of the pit proceeds. After 

 the surface of the marl is uncovered for the full size intended for 

 the area (which ought to be at least large enough for carts to turn 

 about on), a little drain of three or four inches wide, and as many 

 deep (or the size made by the grubbing-hoe used to cut it), should 

 be carried all around to intercept the surface or spring-water, and 

 conduct it to the main drain. The marl will now be dry enough 

 for the carts to be brought on and loaded. But as the digging 

 proceeds, oozing water will collect slowly ; and, aided by the wheels 

 of loaded carts, the surface of the firmest marl would soon be 

 rendered a puddle, and next a quagmire. This may easily be pre- 

 vented by the inclination of the surface. The first course dug off 

 should be much the deepest next the surface drain (leaving a mar- 

 gin of a few inches of firm marl, as a bank to keep in the stream), 

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