FA11T 3.] 
Theobald: Axial group in Western Prone. 
79 
The Kattunga sandstone is of moderately coarse texture. Although the stone is firm, the 
binding ingredient is in small proportion; there is a sprinkling of white clay, but not 
sufficient to fill the interstices of the grains ; the stone thus remains a freestone, dressing 
well under the chisel. From a cursory examination made by Mr. Tween, the cement would 
seem to be a slight infusion of silica; it is unaffected by ordinary solvents. The stone of 
the other hills is somewhat finer in graiu, with a full proportion of matrix, which, under the 
indurating action, assumes a porcellanic state. This highest induration seems confined to 
the parts along the few irregular joints that occur, but in the interior of the rough masses 
the stone is still quite as hard as that of Kattunga. 
From top to base of the Kattunga hills there is no sign of bedding. The lamination 
is, however, betrayed by slight variations in texture, showing the original lie of the rock and 
its undisturbed horizontality. There is no such massive bedding in the sandstone of the 
other hills; even shaly partings are not unfrequent. 
Such differences of texture, structure, and homogeneity might go far to explain the 
exceptional feature in the Kattunga rock; hut there is a peculiarity in its position that is 
worthy of notice in this connection. The main area of the formation lies to the south-south- 
east; and in the low ground to the north of the quarries the soft sandstones and shales are 
again found in well-sections under the alluvium; but at a short distance to the west there 
is a range of granite-hills, on the continuation of which, prolongations and inliers of the 
grauite weather out for some distance in the low ground close to the south of the quarry- 
hills. Thus it seems highly probable that the sandstone here is throughout underlaid almost 
immediately by the granite. At one spot this is fully seen, where a small promontory of 
sandstone crosses to the west of the city-branch of the Nagpur road, and rests upon a 
knoll of grauite. Directly coating the uneven surface of the granite there is here seen a 
variable bed of coarse arkose, now in a rusty and friable state ; its surface is conglomeritic. 
Upon this rests a two-feet bed of a very peculiar rock—a coarse mixed sandstone with an 
excess of earthy matrix in a highly indurated, porcellanic, condition; the whole shivered 
into most irregular blocks. This same quartzite is very extensively found along the base 
of the formation as a contact-rock; hut it also occurs near the boundary between soft earthy 
beds. In the section under notice it is immediately overlaid by a remnant, some fifteen feet 
thick, of the highly jointed sandstone. The hard but unjointed sandstone of the other locali¬ 
ties rests upon a considerable thickness of the unconsolidated sedimentaries. May it not 
he that the shrinkage in the latter cases was satisfied to some extent by external yielding; 
whereas in the Kattunga rock it had all to he accounted for within the mass P 
Although there is much reason to believe that the directions of those joint-systems 
were determined in accordance with the law expounded by Professor Haughton, it is neces¬ 
sary to suppose that even the Primary joints were here developed from a latent state by 
the same conditions that produced the main jointing, the compressing force not having 
been sufficient directly to complete this cleavage-jointing. 
20 (h May, 1872. II. B. MEDLICOTT. 
A PEW ADDITIONAL REMARKS ON THE AXIAL GROUP OF WESTERN PrOME, by W. THEOBALD 
Esq., Geological Survey of India. 
Since the publication of my remarks on the axial group of Western Prorne, in the 
Becords of the Geological Survey, No. 2, 1871, the more extended examination of the neigh¬ 
bouring country has made it necessary to restrict the group within somewhat narrower limits 
than I had at first assigned to it; and I think I shall best convey an idea of the extent and 
scope of such limitation by briefly sketching the various steps by which our knowledge of 
these beds has been acquired. 
