352 BULLETIN OF THE BUSSEY INSTITUTION. 
brought into commerce from the so-called natron-ponds of Egypt, 
which are situated in the desert some thirty or forty miles from the 
Nile and not very far from the mouth of that river. The desert 
in this vicinity was at one time covered by the sea, and it is still 
charged with common salt as well as with carbonate of lime. Once 
a year, when the Nile is full, the desert soil is percolated by the 
river-water which dissolves out the sodium carbonate that has re- 
sulted from the reaction of the salt on the limestone and carries it 
forward to the depressions known as the natron-ponds, from which 
it is taken some months afterward when the Nile has fallen and 
the water in the ponds has had time to dry up. It was noticed 
long ago by Clouet* that if powdered chalk be mixed with sand 
that has been moistened with a solution of chloride of sodium, and 
the mixture be left in contact with the air, an efflorescence of car- 
bonate of soda will soon appear on the surface of the sand. As 
Boussingault puts it: ‘‘ Thus by the conjoint effect of capillarity 
and the carbonic acid of the atmosphere (or that in the pores of the 
soil), common salt in the conditions above mentioned undergoes 
by contact with chalk a partial decomposition, of which the result 
is carbonate of soda, —a salt, like carbonate of potash, most fa- 
vorable to the growth of plants. Accordingly, in furnishing sea- 
salt to a soil sufficiently calcareous, we really enrich it with car- 
bonate of soda. We moreover perceive that the same salt diffused 
through land devoid of carbonate of lime may not produce any fer- 
tilizing effect.” So too Sir Humphrey Davy,f early in this cen- 
tury, remarked as follows in his lectures on agricultural chemistry : 
‘¢ In soapers’ waste from the best manufactories there is scarcely a 
trace of (soluble) alkali. Lime moistened with sea-water affords 
more of this substance, and is said to have been used in some cases 
(by farmers) with more benefit than common lime.” Girardin in 
France and Geubel in Germany t have in like manner insisted that 
salt which has been applied as a manure often reacts on lime in the 
soil with formation of carbonate of soda which favors the growth 
of crops. 
Reinders,§ in his turn, in reporting his studies of the influence of 
* Boussingault’s ‘‘ Rural Economy,” p. 336 of the New York edition of 1865. 
+ ‘*Elements of Agricultural Chemistry,” p. 232 of the Philadelphia edi- 
tion of 1821. 
¢ Cited by Peters in ‘‘ Steckhardt’s Chemische Ackersmann,” 1861, 7. 
pp. 32, 88. See also Heiden’s ‘‘ Diingerlehre,” 1868, 2. pp. 496, 617. 
§ ‘Die landwirthschaftlichen Versuchs-Stationen,” 1876, 19. 197. 
