1821.] Geological Society. 149 



secondly, that their urine is not at all analogous to that of other 

 animals of the order amphibia, being very dilute, containing urea 

 and certain salts, but no appreciable quantity of lithic acid. 

 This peculiarity of urine, so well adapted to the size and struc- 

 ture of the bladder, is the more remarkable, as the favourite food 

 of these animals is the same as that of small lizards, whose 

 urine is of a butyraceous consistence, and nearly pure lithic 

 acid. Hence, and from other facts mentioned by the author, he 

 adduces the conclusion that the nature of urine, in every instance, 

 depends much more on the peculiar action and structure of the 

 secreting organs than on pecuharities of diet, or of the circulat- 

 ing fluids. 



At the same meeting, a paper, by Capt. Kater, was read, 

 entitled " An Account of the Comparison of various British 

 Standards of Linear Measure.'' 



Jan. 25. — The reading of the Bakerian lecture, by Captain 

 Kater, on the form and the kinds of steel most proper to be em- 

 ployed in making magnetic needles, was commenced. 



At the same meeting was read, " An Account of a Micro- 

 meter made of Rock Crystal," by G. Dollond, FRS. 



The improvement consists in making a sphere of rock crystal, 

 and applying it in the place of the usual eye glass of a telescope, 

 and from its natural double refracting property rendering it use- 

 ful as a micrometer. 



Ja7i. 5. — A paper on the Geology of the North-eastern Border 

 of Bengal, by H. T. Colebrooke, Esq. VPGS. &c. was read. 



The Brahmoputra river, which unites its stream v/ith the Ganges 

 at a short distance from their common junction with the sea, after 

 a long course in the Himalaya, passes through the mountains of 

 Aslam, and issues into the plain at the north-east corner of Ben- 

 gal. At that position is a hill at Jogigopha,' which is connected 

 with the Rhotan mountains, and which consists chiefly of a large 

 hemispherical mass of gneiss having strata, or rather masses, of 

 granite on the north-eastern and western sides. 



On the opposite or southern bank of the river is the hill of 

 Pagnalath, which also appears to be composed of gneiss, the 

 masses running from N.E. to S.W. at an angle of 45°. 



At Givalpara, a few miles to the east of Paglanath, granite is 

 found. 



The same rocks occur again at Dhabui, a low hill, partly 

 covered with alluvial soil, near the confluence of the Gadadhar. 

 Blocks of primitive greenstone are also met w^ith here in various 

 parts of the bank of the river. At the confluence of the Kelanke 

 river, which issues from the Garo hills, a little lower down is a 

 precipitous bank, exhibiting graphic granite, and gneiss. 



In the bed of the river, blocks of compact felspar, primitive 

 greenstone, and quartz, united with felspar and hornblende, are 

 found. 



