J()8 ON RAIN, EVAPORATION, &C. 



Experiment on a In order to afcertain this point more fully, and to investigate 

 fhewtoT m uch tne ori g In of fprings, my friend Thomas Hoyle, jun. and felf, 

 water ran off the pracli fed an expedient as follows, beginning in the autumn of 

 Suchftnkfa • 1795 * HavIn § g ot a cylindrical velTel of tinned iron, 10 

 and how much inches in diameter and three feet deep, there were inferted 

 evaporated. j n j j t tvvo pjp es turned downwards for the water to run off 

 into bottles : the one pipe was near the bottom of the veiTel ; 

 the other was an inch from the top. The veflel was filled up 

 for a few inches with gravel and fand, and all the reft with 

 good frefh foil. It was then put into a hole in the ground, 

 and the fpace around filled up with earth, except on one fide, 

 for the convenience of putting bottles to the two pipes ; then 

 fome water was poured on to fadden the earth, and as much 

 of it as would was fufTered to run through without notice, by 

 which the earth might be confidered as faturated with water. 

 For fome weeks the foil was kept above the level of the upper 

 pipe, but latterly it was conftantly a little below it, which 

 precluded any water running ofF through it. Moreover, for 

 the firft year the foil at top was bare ; but for the two laft years 

 it was covered with grafs the fame as any green field. Things 

 being thus circumftanced, a regular regifter has been kept of 

 the quantity of rain water that ran off from the furface of the 

 earth through the upper pipe (whilft that took place) and alfo 

 of the quantity of that which funk down through the three 

 feet of earth, and ran out through the lower pipe. A rain-* 

 gage of the fame diameter was kept clofe by to find the quan-> 

 tity of rain for any correfponding time. 





The 



