On Draining. 



517 



a less perfect system, than is supposed to be requisite, did not 

 daily experience oppose such a conclusion. We must, therefore, 

 endeavour to reconcile this seeming incongruity, and deduce at 

 the same time from the facts disclosed such data as may guide us 

 in determining the essential requisites to ensure completeness of 

 effect in drainage. 



Now, although there can be no reason to question the accuracy 

 of the experiments on filtration made by Mr. Dickinson, and 

 recorded in the Journal of the Royal Agricultural Society of 

 England, vol. v. part i., yet there is a very considerable differ- 

 ence in the aggregate result, as shown by them and the account 

 before us. " The first important fact disclosed," says the com- 

 mentator, page 148, " is that, of the whole annual rain, about 

 42^ per cent, or 1 l-j-V inches out of 26-rVj have filtered through 

 the soil ;" whereas in the Holmfield House experiments there is 

 only shown, as we have already said, 4" 82 inches out of 24 '60, or 

 about 5yV P^r cent, against 42i per cent. This is certainly a 

 very great and somewhat irreconcilable difference in the result of 

 two experiments made professedly to ascertain the same fact. 

 Now, on referring to the ' Memoirs of the Literary and Philoso- 

 phical Society of Manchester,' vol. v. part ii., you will find a paper 

 on rain, evaporation, &c., from the pen of the celebrated Dr. John 

 Dalton (the father of the science of meteorology), wherein he ex- 

 plains a series of experiments made by himself and his friend Mr. 

 Thomas Hoyle junior, to ascertain the amount of evaporation and 

 filtration, and giving the following table of results, viz. : — • 



" Having got a cylindrical vessel of tinned iron, 

 VOL. X. 



says the Doctor, " 

 2 M 



ten 



