On the Composition of Waters of Land-Drainage. 133 



agriculturists, and which are of special interest to the scientific 

 inquirer into the rationale of particular agricultural practices. 



It is not, therefore, necessary for me to allude to the numerous 

 analyses of waters of land-drainage which have been made by 

 xnyself and other chemists, mainly with the view of ascertaining 

 the fitness of the water for drinking and household purposes. 



The object of the present contribution to the ' Journal ' of the 

 Society is mainly to give an account of the results of no less 

 than seventy complete analyses of land-drainage water having an 

 accurately recorded agricultural history. This investigation has 

 occupied me more or less for a period of three years ; and as the 

 results obtained are of considerable importance in a practical 

 point of view, I am anxious to record them in detail, even 

 at the risk of trying somewhat the patience of the reader. 



The seventy samples of water which, as just mentioned, have 

 an accurately recorded history, were kindly supplied to me by 

 Mr. Lawes of Rothamsted. I feel much indebted to that 

 gentleman and to Dr. Gilbert for sending me from time to 

 time drainage-water from various plots of the experimental 

 field at Rothamsted, which for more than twenty-five years has 

 borne wheat from year to year in succession, thus giving me 

 the opportunity to investigate the question of land-drainage, 

 hy supplying me with a series of drainage-waters which I 

 could not possibly have obtained anywheie else under such 

 favourable circumstances, inasmuch as an accurate account has 

 been kept for more than twenty-five years of the kind and quan- 

 tities of manure which each experimental plot of the wheat-field 

 has received from year to year. A full record of the agricultural 

 history of the experimental wheat-field will be found in Messrs. 

 Lawes and Gilbert's classical report " On the Continuous Growth 

 of Wheat for Twenty Years in Succession." * 



The Broadbalk field, Rothamsted, is divided into a number 

 of plots, each experimental plot occupying the space of two-thirds 

 of an acre. It had grown wheat from year to year since 1844, 

 and the different plots had been variously treated as regards 

 manure. 



By opening holes at the end of each drain, passing right 

 through the middle of each experimental plot, the opportunity 

 was given to collect separately the drainage from thirteen different 

 plots. 



These plots were treated as regards manure as follows : — 



Plot 2. — Farmyard-manure every year, 14 tons. 



Plots 3 and 4. — Unmanured every year. 



Plot 5.— Since 1858, 200 lbs. sulphate of potash, 100 lbs. 

 siulphate of soda, and 100 lbs. sulphate of magnesia ; for crop of 



* ' Journal of the Koyal Agricultural Society,' vol. xxv. pp. 93 & 449. 



