PART 1.] 
Alluvial deposits of the Irawadi, Sfe. 
17 
Reference has already been made to the different lithological character of the rocks 
occurring in the southern part of the Sripermatoor area and to the absence of sections 
by which to determine the relationship of the two sets of beds. The series of beds here 
met with consists of white, grey-buff and black sandy clays, and brown, buff, reddish-purple 
and white gritty sandstones. One of the pale-buff sandy clays contains remains of 
Paheozamia and Stanflerites. None of the sections show the base of the series. Prom 
its topographical position and petrological character 1 am inclined to think that this series 
Underlies the great “plant-shale” bed. 
Of very similar character and probably occupying the same relations to the “ plant- 
shales” is a series of gritty sandstones and shales exposed in a fine section made by an 
artificial channel running into the great Chumbrumbaucum tank on its north side. As 
this section lies two miies outside of the Sripermatoor area and the intervening space is 
obscured by the laterite, the position of the series here seen relatively to the “plant-shales” 
can only be guessed at. The Rajmahal character of these beds is proved by the finding of a 
fragment of a Dictyopteris in one of the lower beds of shaley sandstone. 
To the south-west of the Sripermatoor area the Rajmahal series appears to extend to 
some four miles beyond Conjeveram, for shaley and sandy beds of precisely similar character 
underlying the Conjeveram gravels are to he seen in several well sections. The most westerly 
point at which unquestionably Rajmahal plant remains were found was one mile to the south¬ 
west of Rajah’s Choultry. 
In conclusion I may point out that these Rajmahal beds of the Madras area contrast in 
several respects with those of Bengal and Cutch. The Madras Jurassic, or Rajmahal, beds 
contain no carbonaceous matter, which in their equivalents in other parts of India occurs so 
largely as to form coal seams. Nothing but silicified wood has been found in the Madras beds, 
and unlike the Bengal beds, in the Rajmahal hills, with their great intercalated trap flows and 
the Cutch beds, which are overlaid by trap flows of tertiary age, the Madras series is nowhere 
penetrated by, or overlaid by, igneous rocks of any kind, nor in the least, degree metamorphosed. 
Another contrast, hut of less importance, is, that unlike the Cutch beds, which are often of gay 
and bright colors, the Madras beds are remarkable for the dullness and sobriety of their 
coloring, a remark which applies also to their representatives in the Trichinopoly and 
Nellore districts. 
The Sttbmetamoephic and Metamoephic Rocks. 
These demand hardly any notice in this place. The younger or sub-metamorphic series— 
the Kuddapah group—does not come within the area treated of, except in one, and that possibly 
a doubtful case (see page 11). The metamorphic rock series—the gneiss of Southern India— 
also presents little of interest locally; near the coast it consists of alternating hands of 
quartzo-felspathic and hornblendic beds which run to some extent parallel with the coast line. 
Further inland to the westward of the laterite and Rajmahal areas, the gneiss is more 
highly crystalline and largely granitoid or syenitoid in structure, and is traversed by a few 
trap dykes intruded prior to the deposition of even the Kuddapah rocks. 
On the alluvial deposits of the Ikawadi, moee pauticulably as contrasted with 
those of the Ganges,— by W.u. Theobald, Junb., Esq., Geol. Survey of India. 
It may fairly be presumed that the origin and growth of those extended alluvial 
deposits, forming the plains through which the more important rivers, oarve their way to 
the sea, were, in each several case, vei’y similar, and that the history of the deposition of the 
“loess” of the Mississippi valley was but little different from that of the “ loess” of the 
Rhine. Each river system of course has its particular history, recorded in the alluvial 
deposits of its basin, which, in some cases, afford a simple, in others an intricate, record of the 
geological vicissitudes the area has undergone, and in tracing this record we are not un- 
frequently brought in contact with problems far more intricate and extensive in their 
hearing, than the apparently uninteresting character of the beds would suggest, and we have 
here in India in the “loess” of our larger river basins, the same phenomena to account for 
which have so exercised the ingenuity of Geologists in the Case of the “ loess” of the Rhine 
