172 HOW CROPS FEED. 
moving saline matters from thcir solutions in water. Lord 
Bacon, in his “Sylva Sylvarum,” 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 another, and yet it hath 
not lost its saltness as to become potable;” but when 
“drayned through twenty vessels, hath become fresh.” 
Dr. Stephen Hales, in a paper read before the Royal 
Society in 1739, on “Some attempts to make sea-water 
wholesome,” mentions on the authority of Mr. Boyle God- 
frey that “sea-water, being filtered through stone cisterns, 
the first pint that runs through 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 by tlhe sand of certain quantities 
of the salt operated upon.* 
Action of Humus on Saline Solutions.—Heiden (Hoff- 
mani’s Juhresbericht, 1866, p. 29) found that peat and 
various preparations of the humic acids, when 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 that humus, artificially prepared by the 
* These statements of Bacon, Hales, Berzelius, and Matteucci, are derived 
from Prof. Way’s paper ‘*On the Power of Soils, etc.” (Jour. Roy. Ag. Soc. @ 
Eng., XI, 216.) 
