PART 3.] 
Medlicoit: Joint-systems at Jabalpur 
77 
off Maskat (2,000 fathoms) may point to a general and long continued subsidence along 
this coast, and, if so, it is curious to contrast it with the evidence of comparatively recent 
elevation on the opposite shores of Persia as noticed in a previous paper. 
Camp Gwadab, Biluchistan ; 7 
January, 1872. J 
An example op local jointing, by H. B. Medlicott, M. A., F. G. S., Deputy Superin¬ 
tendent, Geological Survey of India. 
Within the cantonments of Jabalpur, south of the civil station and of the city, there 
is a small group of hillocks, or steep bare roclc-masses, about fifty feet in height. The whole 
stand within an area of nearly one hundred and fifty acres, of which the protruding rock 
occupies about two-thirds, in three principal masses. They are locally known as the 
Ivattunga quarries; the sandstone being much valued and extensively worked for building 
stone. Its use for this purpose is greatly facilitated by the very perfect jointing by which 
the rock is traversed. The unique character of this feature in the great formation to which 
the sandstone belongs, and the peculiar petrographical circumstances of the rock in this 
locality, give some interest to the case as suggesting definite conditions to which the jointing 
is due. There is nothing new in the main cause thus educed, but so well-marked an instance 
of local action, or of secondary influences, may be worth recording. , 
The sandstone belongs to an upper member of a great series of rocks representing a 
well-defined period in the geology of India, beginning with the glacial deposits of the 
Talchir group, upon which rest the coal-measures, and ending with various groups hitherto 
included under the name Mahadeva. These strata, as a whole, are hut partially indurated 
and only slightly disturbed. Jabalpur stands upon a boundary of the formation running con¬ 
tinuously for 350 miles in an east-30°-north direction, along the valleys of the Narbada 
and tbe Son. In this neighbourhood the massive sandstones, irregularly associated with 
pale shady clays, are even softer than usual, weathering with well rounded outcrops and 
an undulating surface. It is difficult at first sight to believe that the sharply edged, cliffed 
rocks of the Kattungii hillocks can belong to the same formation. Looked at from the north- 
north-west or the south-south-east they would be taken for well-bedded vertical quartzites. 
In the annexed diagram (Fig. 1) a number (56) of observed hearings of the joint-planes 
are tabulated. Excluding only seven bearings, all in the north-east quadrant, the remainder 
WORTH 
Fig. 1,—Diagram showing bearings of joints in the sandstone of ICattnnga, Jabalpflr. 
