Composition of Waters of Land- Drainage and of Rain. 129 



Reverting; now to our previous calculations, we find that on 

 the supposition of a rain-fall of 25 inches (which we have found 

 to be equal to 5G7,168 gallons, or 2532 tons), and further 

 granting; that the averagje annual filtration is equal to 42'4 per 

 cent, of the whole, we shall have a quantity of 240,479 gallons, 

 or about 1073^ tons passing into the drains. 



Such being the quantity of water which probably represents 

 the minimum running away in any one year by drainage, we have 

 now to consider — 



2nd. The Composition of this icaf.er. — Analyses of drainage 

 waters more or less complete have from time to time no doubt 

 been made by different chemists ; hardly, however, it would seem. 

 Avith the objects which we have at present in view.* The only 

 recorded instance which I have been able to find is that of an 

 analysis by Mr. John Wilson, now professor of agriculture in the 

 university of i^'dinburgh. 



In the autumn of last year, through the kindness of Mr. Dyke 

 Acland, Mr. Wren Hoskyns, and Mr. Paine of Farnham, I ob- 

 tained samples of drainage water from their different localities.! 

 It will no doubt be supposed that in commencing an inquiry of 

 this kind one would naturally make a selection of different soils ; 

 of the same soils under different treatment as to manures, &c. ; of 

 different depths of drainage and varying climate. My answer is, 

 tliat to accomplish such an extensive plan as this — although 

 indeed it may ultimately be very desirable — would, not to speak 

 of difhcnlty and expense, require years rather than months, and 

 that a preliminary inquiry, such as I have now the pleasure of 

 placing before the readers of this Journal, far from tending to 

 mislead, will clear off many of the uncertainties of the question, 

 and leave the points of future research far less numerous and 

 oijscure. For the reason that the waters were collected under 

 his own eye, that his agricultural operations are most carefully 

 recorded, and that his land is farmed very iiiglily, and would cer- 

 tainly afford a maximum of effects as referable to drainage, I 

 have employed the time at my disposal to make a more perfect 

 examination of the waters collected by Mr. Paine than of any 

 others ; which latter, however, I shall have occasion to recur to 

 at another o])portunity. 



Before giving the results of these analyses, I would state, for the 

 information of the general reader, that the analysis of samples of 



* T have, on several former occasions, examined the waters of land-drainape, 

 with the view of asccrtaininjj whether, in tiie particiiliir instances, tiiey were fit 

 fur domestic use, for which tiiey are fVc<|ueutly employed. 



f Several other pentlemen, amongst whom I may mention Mr. Pailcy Denton, 

 Mr. Girdwood, and Mr. Scott, were {;ood enough to furnish me with samples, 

 which as yet I Lave not had time or op[iorlunily to examine. 



VOL. XV H. K 



