563 



J, G. MalcolmsoNj Esq., on the Fossils of 



less elevated and the trap breaks through the granite and stratified rocks, 

 while to the west the mountains are, with a few exceptions, entirely composed 

 of basalt from the level of the sea to the loftiest summits. 



Lonar Lake,^c. — The Sichel hills, which have heretofore attracted little at- 

 tention in a geological point of view, terminate to the west in the neighbour- 

 hood of Lonar, near what appears to have been a vast crater in the centre of 

 the great basaltic district. As it is the only instance of a volcanic outburst 

 discovered in this immense Plutonic region, a more detailed account of it than 

 has yet been given to the public, may not be unacceptable*. 



It is a nearly circular or oval depression, in a country composed of tabular and nodular basalt, 

 and sloping gently towards it on every side. It is between three and four miles in circumference at 

 the upper margin of the precipitous escarpment which rises from the bottom of the valley about 

 500 feet. The extent from which the water is collected may be about six miles in circumference, 

 but no measurements were made. Two small streams fall into it from above ; one issuing from a 

 pagoda, to which it is carried from the gentle slope behind ; and the other passes over a small cliff. 



on which it deposits a considerable quantity of stalactite. The sides of the crater are covered with 

 a forest inhabited by tigers and game ; and the bottom is occupied by underwood, a few fields, in 

 the irrigation of which the water of the streams is nearly expended, and by a small lake of salt 

 and bitter, greenish water, surrounded by a muddy shore, and varying in size at different seasons. 

 Many sweet springs issue from the saline mud, and a well is built within its highest level, the 

 water of which stands at the same height as that of the lake, though issuing from a depth of nearly 

 twenty-four feet. 



I have carefully examined the water of this well, and that of tiie small stream at the pagoda 

 above. This last had a specific gravity of 1000'6 ; and 2000 grains, evaporated at 212°, gave a 

 solid residue of -i^ of a grain, the greater part of which consisted of muriate of soda with a little 

 sulphate, and the remainder of carbonate of lime. The water of the well below had nearly the 

 same specific gravity, but contained in 2000 grains, one grain of solid matter, of which -ttj of a 

 grain were soluble in water, and contained muriate of soda and a little sulphuric acid and lime ; the 

 insoluble part consisted of carbonate of lime. Neither of the waters contained any trace of alkaline 

 carbonates or of magnesia. It is unnecessary to go further into the analysis here, as another bot- 

 tle of the same water had a higher specific gravity, and contained more lime, a circumstance suffi- 

 ciently accounted for by the escape of a portion of the carbonic acid from the other specimen. 

 The water of the lake is clear, and has no unpleasant smell; but the mud at its bottom is strongly 

 impregnated with sulphuretted hydrogen. In February, 1834, when the specimens were collected, 

 the lake was in no place more than 5 feet in depth of water and mud, but when full it may be eight 

 or ten feet deep in some parts. A layer of salt 2 or 3 inches thick covered the bottom under the 

 viud, and when broken up and removed, was found to be composed of a middle plate, with radi- 

 ating laminae above, and having a striated appearance below. That obtained by diving and bnng- 



* Captain Alexander has published a notice of this lake in the Transactions of the Literary 

 Society of Madras, and in the Edinburgh Philosophical Journal ; but he must have examined it 

 very cursorily or he would not have overlooked its real nature, and stated it to be unfathomable, 

 when, in fact, the water is everywhere shallow. An extract from a private letter to Mr. Prinsep, 

 and published in his Journal for June 1834, was written before I had myself examined the che- 

 mical history of the lake. 



