180 Dr. Marcet on the specific gravity and temperature 
some account of the saline matter contained in the waters of 
Lake Ourmia. I Shall only state at present that the specific 
gravity of the specimen of water in my possession, which 
appears to have been very carefully preserved, is no less than 
1165,07, a degree of saline impregnation which has not, I 
believe, been observed in any other lake, with the exception 
of the Dead sea, the waters of which are even heavier. 
The excellent .opportunities which occurred, during the 
late northern expeditions, for procuring specimens of water 
from the various kinds of ice which are met with in those 
regions, and the obliging zeal of its commanders, afforded 
me the means of making some inquiries into the nature of 
these waters. With regard to the floating masses of ice 
called icebergs , which are formed from the waters of melted 
snow, and are detached by rain and torrents, or by their 
own weight, from the vallies and from precipitous rocks along 
the shores, it was long known that they consist of fresh 
water, in a state of great purity, though perhaps seldom so 
perfectly pure as the specimen marked 63 (Table IV.), the 
specific gravity of which was exactly 1000. But the immense 
fields of ice, or fioes, which are formed from the actual con- 
gelation of the surface of the sea, are of a different descrip- 
tion. This ice, generally speaking, is not so compact or so 
transparent as the icebergs, and it is even stated, in a late 
curious and elaborate dissertation on the subject of the polar 
seas, published in the Edinburgh Review,* that this ice is 
* ‘ Edinburgh Review’, vol. XXX. page 15. There is also in the 4th volume of 
the * Journal of Science and the Arts,’ a paper of Mr. Scoresby, which was read in 
18x5, before the Wernerian Society, and contains many curious and valuable obser- 
vations. 
