382 
SALINE DEPOSITS FROM IRRIGATION. 
tain force of h} r drostatic pressure to tlie water witli which the 
rice is irrigated, and the infiltration from these fields is said to 
extend through neighboring grounds, sometimes to the distance 
of not less than a myriametre, or six English miles, and to he 
destructive to crops and even trees reached by it. Land thus 
affected can no longer he employed for any purpose hut grow¬ 
ing rice, and when prepared for that crop, it propagates still 
further the evils under which it had itself suffered, and, of 
course, the mischief is a growing one.” * 
The attentive traveller in Egypt and Nubia cannot fail to 
notice many localities, generally of small extent, where the 
soil is rendered infertile by an excess of saline matter in its 
composition. In many cases, perhaps in all, these barren spots 
lie rather above the level usually flooded by the inundations 
of the Nile, and yet they exhibit traces of former cultivation. 
Recent observations in India, a notice of which I find in an 
account of a meeting of the Asiatic Society in the Athenaeum 
of December 20,1862, No. 1834, suggest a possible explanation 
of this fact. At this meeting, Professor Medlicott read an essay 
on “ the saline efflorescence called £ Reh 5 and 6 Kuller,’ ” 
which is gradually invading many of the most fertile districts 
of Northern and Western India, and changing them into sterile 
deserts. It consists principally of sulphate of soda (Glauber’s 
salts), with varying proportions of common salt. Mr. Medli¬ 
cott pronounces “ these salts (which, in small quantities are 
favorable to fertility of soil) to be the gradual result of concen¬ 
tration by evaporation of river and canal waters, which contain 
them in very minute quantities, and with which the lands are 
either irrigated or occasionally overflowed.” The river inun¬ 
dations in hot countries usually take place but once in a year, 
and, though the banks remain submerged for days or even 
weeks, the water at that period, being derived principally from 
rains and snows, must be less highly charged with mineral 
matter than at lower stages, and besides, it is always in mo¬ 
tion. The water of irrigation, on the other hand, is applied 
* VItalic & propos de VExposition de Paris, p. 92. 
