THE PHENOMENON OF ABSORPTION IN ITS 



PvELATION TO SOILS. 



A RESUME OF THE SUB.JECT. 



By JAMES ARTHUR PRESCOTT. 



{Rothamsted Experimental Station.) 



The facts of Absorption. 



It has been known from the earliest times that soils would remove 

 salts and colouring matters from solution and the problems arising 

 out of the observations made on this phenomenon were among the 

 earliest to be attacked by agricultural chemists. It was known to 

 Aristotle that sea water lost some of its taste by filtration through 

 sand and this observation seems to have been confirmed and applied 

 in many ways. Lord Bacon in his Sylva Sylvarum^ discussed the ques- 

 tion of making sea water potable by filtering through sand. Le Comte 

 de Marsilli^ made quantitative experiments. Sea water was filtered 

 through fifteen successive vessels of garden soil and a diminution in 

 the salt content was proved by evaporation and by the change in 

 specific gravity. Similar results were obtained with sand. Boyle 

 Godfrey^ discussed the question of making sea w^ater fit for use on ships 

 and observed that if sea water be put into a stone straining cistern 

 the first pint that runs through will be like pure water, having no taste 

 of salt, but the next pint wdll be as salt as usual. Stephen Hales* in 

 dealing with the same question refers to the use of a soft stone by the 

 Dutch as a filtering material, but he points out that this method has 

 no practical value as only the first portions of the filtrate are free from 

 salt. 



1 §§ 1 and 882. 



^ Histoire physique de la Mer, 1725 



^ Miscellaneous Experiments and Observations, 1737. 



* Philosoj)hical Experiments, 1739. 



