300 Voysey’s Report on the Geology of Hyderabad. [Junz, 
4th. The concentric lamellar and distinct concrete structure; the 
great facility of decomposition; the rounded appearance of the decom~ 
posed masses, logging stones, and tors. 
5th. The numerous lakes or tanks spread all over the country, some 
of which are of very large dimensions. 
Ist. The granite israrely seen in ranges until a near approach to Hy- 
derabad ; when it first appears after crossing the Kistnah, it is seen 
principally in rounded blocks, scattered without order, and in flat masses 
of large dimensions, very little elevated above the surface. These how- 
ever increase in size and height as we proceed to the north westward, 
where in the waving plain, in which the two remarkable hills of Nelgondah 
are situated, numerous rounded isolated hills are seen spread over it in 
every direction, unconnected even by their bases. The hill of Nelgon- 
dah presents the first approach to the continued range; its summit is 
about 1000 feet above the plain, declining gradually to the north-west 
until it reaches that level. At Mulkapur more regular granitic ranges 
in the same direction appear, and are continued to Hyderabad, not 
without frequent interruptions, and the interposition of large isolated 
mountains of solid granite. Here, however, it must be observed, the 
granite assumes a new character, derived from the numerous logging 
stones and tors of the most grotesque figures and extraordinary posi- 
tion. The origin of these logging stones may be traced to the tors, 
which are masses of tabular granite, generally not more than two or 
three in number, the interstices of which, admitting therain, subject the 
granite to a more rapid decomposition in those than in other parts of 
the masses, and ultimately give them the rounded forms and tottering 
bases* observed. 
It may be asked, wherefore other rocks, such as greenstone and 
basalt, do not assume similar appearances in decomposition ? It is pro- 
bable that a sufficiently satisfactory reason may be assigned in the 
different directions: of their interstices, which in the granite are hori- 
zontal, whilst in the above-named rocks they are vertical. 
The last place to north-west where these logging stones were ob. 
served is Béchktnda, in latitude nearly parallel to Oudgir, and not far 
distant from the place where the granite becomes every where covered 
by the trap. 
Three formations of quartz rock have been observed, viz. at Secan- 
derabad, Jogipet, and Pitlam, the base of the whole being granite. That 
* See description of the logging stones in Cornwall, in the Transactions of the 
Geological Society. 
