PART 3.] 
Theobald: Occurrence of erratics in the Potwar. 
141 
Indeed, my present evidence goes farther than that of the so-called and so-disputed Kangra 
erratics and moraines, for in their case I merely argued for a terrestrial or moraine origin 
which did not exclude the probability of a sufficiently great difference of level in the whole 
country to largely obviate the isothermal difficulty, whereas I now am forced to contend for 
floating ice as the vehicle of my Potwar erratics, and this almost precludes the idea of any 
considerable difference of level between then and now along the Indus basin, the conditions of 
the problem rather necessiting the supposition of the Potwar then forming a vast lake sub¬ 
sequently drained by the lowering of the Indus bed above Kalabagh. 
I will preface my remarks by saying that by the term “erratic,” I understand fragments 
of stone of any size or shape which have been transported by ice, and that the occurrence of 
blocks of stone (neither meteoric nor presumably due to drift timber), embedded in thinly 
laminated impalpable silt, is prima facie evidence of ice as tlie transporting agent. 
The Potwar is that vast spread of undulating open ground north of the Salt Range. 
It is sparingly marked with hills, and rendered somewhat difficult to traverse by deeply 
excavated streams and ravine-ground, the result of atmospheric denudation acting on a soft 
alluvial surface. The surface is mainly alluvial, hut the underlying Siwalik sandstones often 
crop out above the surface, or as frequently display themselves in the deep sections afforded 
by streams and ravines. 
The alluvium—or loess, as it has been proposed to he called by some writers— is very 
variable in character ; most generally it is a brown clay, with little or no IcanTcar (lime-nodules) 
in it, and very prone to melt away before rain action ; hence the deep intricate ravines which 
intersect it. 
In some spots, as south-east of Fatchjang, towards the Khaire-Murut range, it presents 
the character of a lacustrine marl, with thick beds of earthy tufa crowded with land and 
fresh-water shells, among which I remarked — 
Lymnea rufescens L. (probably 
var. of L. peregra). 
Planorbis exustus. 
P. converiusculus. 
Vivipara Bengdlensis. 
Ihjlhinia pulchella. 
Melaida tulierculata. 
Corbieula (a small species near 
Jgrensis). 
Unio (near Candahariea.) 
Macrochlamys Jfyfsquemontii. 
Cylendrus insular is. 
Napeens salsicota.' 
Opeas gracilis. 
At other places where less tranquil deposition was taking place, the alluvium has the 
character of ordinary river deposits, clay, sands, and gravels intermixed; whilst east ot 
Rawalpindi these gravels are replaced by coarse boulder conglomerates with an aggregate 
thickness of over 200 feet, and possibly much more, as denudation has largely modified the 
surface of these beds. 
Near Jand a considerable area exists of a fine thin-bedded silt wholly devoid of 
organic remains, and therein presenting a striking contrast to the equally fine, though 
dissimilar, clay or marl at Fatehjang. A considerable thickness oi this silt is seen (40 ieet 
at least), hut its relation to the ordinary alluvium is obscure, it being covered over and 
masked by enormous quantities of blown sand carried over it tronitbe bed of the Indus by the 
powerful west winds blowing in the hot season. This silt is impalpahly fine and thiu-beddeci, 
and of an extremely pale greenish fawn colour, and in it are impacted masses ol granitoid 
gneiss, such as constitute the biggest erratic blocks of the district about to be enumerated. 
One such block, a little under a foot in diameter, was seen in a road-side section north ot 
Jand, impacted in situ, and but half exposed by denudation in this silt, the fine laminin 
of which were curved against it, as would be in the case ot a foreign body embedded in 
such a position. 
