17^ now CROPS FEED. 



raoving saline matters from their solutions in water. Lord 

 Bacon, in his " Syh^i Sylvarura," speaks of a method of 

 obtaining fresh water, which was practised on the coast 

 of Barbary. " Digge a hole on the sea-shore somewhat 

 above high-water mark and as deep as low-water mark, 

 which, when the tide cometh, will be filled with water 

 fresh and potable." He also remarks " to have read that 

 trial hath been made of salt-water passed through earth 

 through ten vessels, one within anotlier, and yet it hath 

 not lost its s.'iltiiess as to become potable ; " but when 

 "drayned througli twenty vessels, hath become fresh." 



Dr. Stephen Hales, in a paper read before the Royal 

 Society in 1739, on '' Some attempts to make sea-Avater 

 wholesome," mentions on the authority of Mr. Boyle God- 

 frey that "sea-water, being filtered through stone cisterns, 

 the first pint that runs thi'ough will be pure water having 

 no taste of the salt, but the next pint will be salt as usual." 



Berzelius found upon filtering solutions of common salt 

 through sand, that the portions which first passed were 

 quite free from saline impregnation. Matteucci extended 

 this observation to other salts, and found that the solu- 

 tions when filtered through sand were diminished in den- 

 sity, showing a detention l)y the sand of certain quantities 

 of the salt operated upon.* 



Action of Humus on Saline Solutions. — Heidi n {Hoff- 

 man)i''s tTalweshericht, 1866, p. 29) found that peat and 

 various preparations of the humic acids, Mhen brought in- 

 to solutions of chloride of potassium and chloride of am- 

 monium, remove a portion of these salts from the liquid, 

 leaving the solutions perceptibly weaker. The removed 

 salts were for the most part readily dissolved by a small 

 quantity of water. W. Schumacher {Hoff. Jahres., 1867, 

 p. 18) observed tliat humus, artificially prepared by the 



* These statements of Bacon, Hales, Berzelius, and Matteucci, are derivec' 

 from Prof. Way's paper " On the Power of Soils, etc." {Jour. Roy. Ag. Soc. oj 

 Eng., XI, 316.) 



