ON THE GEOLOGICAL STRUCTURE 
XVII. — On the Geological Structure of the 
Hill of Seetdbuldee^ NagpooVy and its imme- 
diate Vicinity. 
By H. W. Vaysey, Esq. 
Surgeon to the Trigonometrical Survey, East Indies. 
vCCommunicated by Sir James Macgrigoh, President of Army Medical Board^^i 
{Read 6th March 1824.) 
The Hill of Seetabuldee, although agreeing in form 
and interior structure with other basaltic hills in its neigh- 
bourhood, merits a more particular description, on account 
of some peculiarities in the composition of the main rock, 
hitherto unnoticed by geologists, and for the opportunities 
afforded by its extensive quarries of studying the varied 
structure of the rocks of the Trap family, which is rarely 
to be seen in so distinct a manner. 
The mass of the hill is composed of porous basalt, with 
a semi-columnar appearance, derived from numerous verti- 
cal fissures. It passes, at some places in a gradual, and at 
others in an abrupt manner, into a coarse porous wacke or 
indurated clay, which in its turn changes, in a similar 
manner, to the nodular basalt or wacke, of which the 
northern and southern summits of the hill are composed. 
