VOL. LXXIII.] PHILOSOPHICAL TRANSACTIONS. 447 



cold is below its freezing point. Such substances as require, in order to melt, a 

 degree of heat much above that of our atmosphere, experience so great a change 

 of temperature on being taken off the fire, that they become solid hastily, and 

 as it were in confusion; whereas quicksiver, having never probably been exposed 

 to a degree of cold much exceeding that of its melting point, its particles have 

 had full leisure to arrange themselves regularly, in exact conformity to the laws 

 of their mutual attractions. As in Prof. Blumenbach's and Mr. Hutchins's ex- 

 periments, so here probably some slight roughness of the surface was occasioned 

 by this crystallization; in consequence of which M. Pallas compared his frozen 

 quicksilver to tin, rather than to bright silver, the appearance it always assumes 

 when congealed in smooth glass. 



Another property of quicksilver, very important to be known, was observed 

 perhaps no were -so distinctly as on this occasion at Krasnoyarsk: viz. its tendency 

 to adhesion in freezing. Thus, Dr. Pallas says the fragments of the congealed 

 mass stuck to each other, and to the bowl in which they lay. So likewise Mr. 

 Hutchins found the frozen quicksilver adhering to his cylinders and gallipot; 

 Professor Blumenbach to his glass vessel; and similar facts occurred to other ob- 

 servers. Hence the deceptions, so often mentioned, from the sticking of the 

 mercury in the stems of thermometers. And this cause of error can scarcely 

 ever fail to take place; for if quicksilver congealing in wide open vessels adheres 

 to them wherever it touches, how can it be expected to remain loose when frozen 

 in a narrow tube? Now, since quicksilver, under these circumstances, retains 

 the same appearance as while fluid, from the polish given to its surface by the 

 smooth glass, it is no wonder that such frequent mistakes have been made rela- 

 tive to the height of the thermometer, both in experiments with artificial cold, 

 and in meteorological observations. At the same time it must be confessed, that 

 such a tendency to adhere, in a metal which contracts so much in becoming solid, 

 is not a little difficult to explain, unless we may suppose it to be the immediate 

 effect of the crystallization. Quicksilver, with all its other qualities of a perfect 

 metal, seems from Dr. Pallas's, and indeed most of the experiments, not to be 

 completely malleable, but rather apt to break under the hammer. Perhaps it 

 has never been sufficiently cooled to possess its metallic properties in perfection; 

 for with respect to its melting point it may be considered as having always been 

 hot, that is, heated near to fusion, a state in which other metals undergo a very 

 sensible change in their properties. But when mercury congeals in vessels which 

 confine its surface, it seems to become more malleable than under a loose crys- 

 tallization. 



Nearly 500 miles south-eastward of Krasnoyarsk is the town of Irkutsk, the 

 capital of a Siberian province on the vast Baikal lake, and situated in lat. 52''^ 

 and about the 104th degree of e. longitude. At the former of these places, the 



