Geology. 327 
GEOLOGY. 
Slate in India.—Mr Oldham, superintendent of the Geological Survey 
of India, has written a long memorandum on the use of slates in India 
generally, and on the slabs of the Kurnool district particularly. After 
explaining, at length, the nature of true slate, namely, that it is ‘‘ capable 
of almost infinite division, thin plates or slabs splitting with tolerably 
even surfaces of considerable size,’’ he goes on to show that the Kurnool 
slabs and the same material found in other parts of India are incapable 
of this infinite division, &c. And he is of opinion that “ the Kurnool slabs 
. referred to by Lieutenant Beckley and the Madras Government are en- 
tirely unfitted for sloping roofs; that they cannot be procured in slabs 
dividing naturally of such size and thickness as would adapt them for such 
roofs ; that sawing them would, even if practicable, be too expensive ; 
that the slabs thus procured would be either too thin to give the requisite 
strength, or, if of sufficient strength, would be too heavy and thick for 
economical or effective use. But for flat roofs or floors he thinks they 
may be used with advantage. Mr Oldham adds,—‘‘ I would further urge 
that such stone slab floors, where the proper material can be procured 
with a moderate amount of carriage, and at a fairly reasonable rate, will 
prove much more durable, economical, more cleanly, and in every respect 
better floors than either wood or ‘ pucka’ for barracks, hospitals, court- 
houses, or any place where there is constant intercourse, and also for the 
verandahs of such buildings. I have just alluded to the cleanliness of 
such floors; and I consider this to be by no means a trifling advantage. 
They can be mopped out with clean water, or washed with soap and 
water in the same way as ordinary wooden floors, and can thus be kept 
sweet, clean, and free from vermin with the smallest amount of labour. 
There are several localities in Bengal and the North-Western Provinces 
where such slabs could be obtained as would be suited for flooring. The 
hills to the south of Monghyr, the Sikkim Hills (poor), the Soane Valley, 
the Kumaon Hills, &c., the Gwalior Hills. But in few cases will such 
materials admit of any great length of carriage; and they can therefore 
only be used economically when procured within a reasonable distance of 
the works where they are required.” 
MISCELLANEOUS. 
The Great Comet of 1861.—On Sunday evening, June 30th, between 
eight and nine o'clock, there was observed at New Haven, in the northern 
part of the heavens, in an opening between the clouds, and at an elevation 
of about ten degrees, anebulous body of unusual brilliancy. Its appearance 
was similar to that of the planet Jupiter shining through a thin mist ; and 
it was nearly as conspicuous an object in the heavens as Jupiter, although 
this was due not wholly to the intensity of its light, but partly to its ex- 
tent of surface, its apparent diameter being about equal to that of the full 
moon. It was at once suspected that this body was a comet; but this 
conclusion was adopted with some reserve, on account of the unusual 
brilliancy and sudden apparition of the meteor. This light was soon 
concealed by a cloud; but about half an hour later, a larger opening in 
the clouds disclosed the tail of the comet, in the form of a bright streamer, 
with sides nearly straight and parallel, and pretty sharply defined. The 
head of the comet was now invisible; but a little later both head and tail 
were seen simultaneously, forming together one of the most brilliant 
comets of the last fifty years, and astonishing every one by the suddenness 
of its development. Mr R. W. Wright of this city marked the position ° 
of the comet’s head upon a star chart as accurately as he was able, and 
hence concludes that about a quarter before nine o'clock, June 80, its 
R. A, was 108° and Dec. 47° N. 
