236 BERTHA/S VISIT TO HER 



between the two upper rows of stones, he has 

 planted quick-thorns, and on the top of the bank 

 a few young gak and elm trees. The deep ditch 

 will serve to carry off the water from some drains 

 that are to be made in a part of the ground 

 which is wet and marshy. These drains are to 

 be covered with earth ; and something must be 

 done to keep them from filling up. Some people 

 line them with stone, but that is too expensive ; 

 and as he has just clipped some of his hedges, 

 he intends, I believe, to put the branches of the 

 thorn-bushes into the bottom of the drains, which 

 will also prevent the sides from falling in. 



Springs are formed in the bosom of the earth, 

 my uncle says, by the rain water which sinks 

 through the surface, and which, gently oozing, 

 or percolating, as he calls it, through the 'sand 

 or gravel, or through other porous strata, con- 

 tinues to descend till it is intercepted by some 

 bed of clay or rock. No longer being able to 

 descend, it follows the course of this impassable 

 bed, and if thus conducted to the outside of the 

 ground, lower down the hill, it forms then a 

 spring. But if prevented oy any obstacle from 

 flowing freely out of the ground, it diffuses itself 

 under the surface, and produces swamps and 

 marshes. My uncle has been of great use to 

 Franklin, not only by teaching him how to dis- 

 cover from the form of the ground where it is 



