18 



DRAINING OF LAND. 



4. The same is true with regard to the inferior temperature, 

 and those below O . 

 A blow will 5. When bodies have the same temperature as mercury, and 

 produce eloc- t j ie conlact produces no electricity, the electric power nay 

 the contacts be excited by means of a smart blow of the body under expe- 

 riment upon the surface of the mercury. This blow is some- 

 times ineffectual when the barometer is low. Here we already 

 see the effect of the barometic pressure upon the electric fluid ; 

 but much more evident proofs will be hereafter shewn. 



(To be concluded in our next,) 



are at equal 

 temperature? 



XIII. 



Plan of the 



ground. 



♦Method of 



m 



Account of the Drainage of a piece of Morass Land, called the 

 Tarn, in the Parish of Clapham, in Yorkshire. By Major 

 B. Hesleden. (Soc. Arts XXX.) 



riOHE plan fig. 2. pi. V, describes the direction in which the 

 JL principal or main drain, as also the cress drains, were 

 severally carried, and A represents a spring of water, B the 

 main drain, CCC, &c. smaller drains, D a small piece of dry 

 ground. 



The land consists of about twenly-one acres, and from its 

 being encompassed on all sides by rising ground, the water was 

 observed to spring from the bottom of the hill j consequently, 

 the first drain was taken along its base and boundary of the 

 Tarn, so as to receive the water on its first approach ; the 

 others were taken in the same direction, some of which; near 

 the outward side, were made at the distance from seven to ten 

 yards j but near the centre, at a greater distance, (viz.) ten to 

 fifteen yards from each other, according to the dryness of the 

 land. The principal, as well as the cross drains, were finished 

 in the best possible manner, the bottom of them being inva- 

 riably flagged, or laid with flat stones, (except in a few instances 

 that happened to be firm clay), previous to its being walled 

 on both sides, or soughed, then covered with flat stone, and 

 afterwards filled to the top with earth and sod, which wouid 

 be above the stone from one foot to half a yard in thickness, i 



This 



