404 ON SIPHONS AND JETS OF \tfATER. 



air vessel, there passed a tube to another reservoir, higher than the 

 original reservoir, and destined for the brew-house. When water 

 was drawn for the kitchen, the water in the pipe acquired, by run. 

 ning, a considerable velocity. Hence, when the stop-cock was 

 shut, it acted on the valve, forced it open, and rushing into the air 

 vessel, compressed the air which it contained. This happening 

 every time that water was drawn for the use of the kitchen, which 

 was very frequently, the water made its way into the brew-house 

 reservoir, and supplied it sufficiently. 



Dr. Darwin, by an application of the same principles, ingeniously 

 obtained an artificial spring from an elevated well at a considerable 

 distance. The following is his account of the plan pursued, as 

 communicated to the Royal Society in 1785. " Near my house, says 

 Dr. D., was an old well, about 100 yards from the river Derwent 

 in Derby, and about four yards deep, which had been many years 

 disused, on account of the badness of the water, which I found 

 to contain much vitriolic acid, with at the same time a slight sul- 

 phureous smell and taste ; but did not carefully analyse it. The 

 mouth of this well was about four feet above the surface of the 

 river; and the ground, through which it was sunk, consisted of a 

 black, loose, moist earth, which appeared to have been very lately 

 a morass, and is now covered with houses built on piles. At the 

 bottom was found a bed of red marl, and the spring, which was 

 so strong as to give up many hogsheads in a day, oozed from be- 

 tween the morass and the marl : it lay about eight feet beneath the 

 surface of the river, and the water rose within two feet of the top 

 of the well. 



" Having observed that a very copious spring, called Saint Alk- 

 inund's well, rose out of the ground about half a mile higher on the 

 same side of the Derwent, the level of which I knew by the height 

 of the intervening wier to be about four or five feet above the ground 

 about my well ; and having observed that the higher lands at the 

 distance of a mile or two behind these wells, consisted of red marl 

 like that in the well ; I concluded, that, if I should bore through this 

 stratum of marl, I might probably gain a water similar to that of St. 

 Alkmund's well, and hoped that at the same time it might rise above 

 the surface of my old well to the level of St. Alkmund's. With this 

 intent a pump was first put down for the purpose of more easily 

 keeping dry the bottom of the old well, and a hole about 2 inches 



