S76 
Records of I he Geological Snrveg of India. 
[VOL. XIII. 
■whicli some deposition of finer sediments occnrs more or less in basin fashion ; 
but they principally become filled nji by the invasion of the river to find a lower 
level; when, at least on the line of the new channels, there must be consider¬ 
able removal and ultimate replacement of any finer sediments. In this way it 
seems probable that in the gi'owth of the river plains, it is rare for any large 
area to escape being traversed by a channel of considerable magnitude, or for 
such areas to be filled up by deposits in which the slojie of the river itself is not 
on the whole maintained. The original usav plains may have been such excep¬ 
tional areas, in which therefore special local obstruction existed to underground 
drainage. It must, indeed, be admitted that the actual subsoil drainage of the 
])lains is usually imperceptible; but this seems to be directly accounted for by 
what is the head and front of the complaint regarding reh: that owing to 
shallow cultivation, to the sun-baked condition of the surface, and to the absence 
of any considerable tree vegetation, the rainfall can only soak to a small depth, 
the remainder running to waste off the surface, or being taken up again by 
evaporation. Tor efficient drainage there must be efficient penetration to supply 
it withal: and, deficient percolation of water through the soil and the .sub-soil to 
the ground beneath is the condition, in default of which the gi'owth of reh is 
inevitable. It would, of course, be easy to imagine circumstances more favourable 
to drainage than are those of the gently-sloping alluvial deposits of these plains ; 
but it seems to me that reh being in part a necessity of the ground structure 
here, cannot bo .sustained. 
8. There remains the condition of climate, which is the active element of the 
combination. It is represented (pai'a. 15) as being analogous to that of the 
typical cases cited, only intensified by heat. Here, again, I have to admit the 
actuality, but as a charge against nature it is even more untenable than the last. 
There is contrast rather than correspondence between the physical suiTOundings 
of India and those of the typically arid tracts mentioned. In these, aridity is 
indeed more or less inevitable, for the life-giving moisture hardly approaches 
them, being to a great extent abstracted from the air currents before they reach 
these areas. But India is on two sides bounded by a reeking caldron of tropical 
ocean ; and on the third there is a great aii’-elcvator, flanked by a huge con¬ 
denser, sending back upon her plains almost every drop of the water that had 
previously floated over them, repelled to a very largo extent by the accumulated 
heat of the bare and parched ground sni’face. The endeavour to make these 
returning waters do duty for rainfall must bo a very p)oor substitute for the due 
reception and conservation of them in this form in the first instance. It can 
scarcely be questioned, that left to nature, every foot of our Indian deserts would 
now have been covered with perennial verdure, and that the present desola¬ 
tion is the result of the devastating pi’oclivitios of a woi-sc than savage mankind. 
It may, too, bo affirmed that with time the blessings of nature might bo restored. 
