RELATIONS OF THE GRITS OF KALTCHEDANSK. 
367 
about a square mile. The best millstones occur in beds from two to three feet 
thick, and are worked from beneath a roof of less valuable grit, where though per- 
fectly horizontal, they have somewhat of a concretionary shape, and are brought 
out in lumps from six to seven feet long, which have olten a rustv-ferruginous, 
occasionally a green exterior. Thin beds of sand and clay (wayboards) fold irre- 
gularly round these concretions, which to some extent reminded us of the tertiary 
“ meuli^res ” of the Paris basin. If we had not first viewed the section at Krasnoi- 
gora on the Issetz, where these beds, regularly and horizontally stratified, lie 
upon the igneous rocks, we should have had some difficulty in believing that they 
were entirely of aqueous origin, so much has the detritus of these quarries a tra- 
chytic and vitreous aspect 1 , and so much did the grating of the debris under our 
feet remind us of some of the trachytes of Auvergne. Hand specimens may, 
indeed, be selected which approach to the character ol pitchstone and the tra- 
chytic grits of Hungary. 
Though the section at Krasnoi-gora on the Issetz exposed the millstone grits 
near the upper surface, yet the ravines at the village of Kaltchedansk showed 
them to be overlaid by forty to fifty feet of thick and thin beds of grey mud- 
stone or claystone somewhat compact, of conchoidal fracture, and covered by 
a bluish and softer finely levigated mudstone. In a pile ol detritus lodged in an 
adjacent hollow, and derived from these beds, we found several fragments of 
amber. 
From the horizontal and undisturbed condition of all these overlying strata, it is 
evident they have been accumulated after the most violent agitations which the 
Ural chain has undergone. Similar beds extend, in fact, far to the north along the 
lowermost slopes of the Ural chain. At Verkhoturie, where they also surmount 
igneous rocks, they have been described by M. Rose, but neither m that tract, to 
which we shall hereafter advert, nor at Kaltchedansk, could we detect organic 
remains in them. On our Map, therefore, we have simply inserted them (under a 
yellowish colour) as tertiary deposits, of the age of which we are ignorant. Some 
persons on account of their imbedded lignite and amber, might argue tor their 
assimilation to the German strata of clay and sands with brown coal. Others may 
conceive they were accumulated in a vast basin of fresh water, which separated 
. These rocks were inaccurately described by M. Tchaikovski as containing Olivine and Leucite. 
They are simply grits made up of fragments of porphyry, and grains of quartz of different colours, m a 
felspathic base. See Journal des Mines de Russie, 1830. 
1 o n 
3 b 2 
