the Quicksilver Mines ofldria in Illyria. 309 



than that of the Idrixa ; there are more cultivable grounds, and 

 particularly meadows, in it. 



Sluices for retaining the water destined for floating the tim- 

 ber necessary for the service of the mines have been made on 

 several of those torrents ; and the French during their short ad- 

 niinistration erected one on that of the Woitschiack, which is 

 distinguished from the rest by its solidity and elegant construc- 

 tion. It was just finislied under the care of General Andreossy 

 when the French evacuated Idiiain 1S13. 



Among the torrents which swell the Idrixa, there are none 

 truly permanent but thos,e of the Canomla and the Zalla, and 

 even the latter is often dry in summer. 



The narrow valley through which the Idrixa flows is bounded 

 by two chains of mountains, the mean height of which measured 

 barometrically is about 288 fathoms. They are in general cal- 

 careous, of the kind called transition. All these calcareous 

 masses are frequently intersected by very much inclined strata 

 of argillaceous schistus, particularly in the environs ofBas Idria. 

 These schists sometimes contain very thin layers of beautifully 

 white laminar quartz, and frequently also carbonated lime. 



In other parts there are schists strongly depressed, reticular 

 and curvilinear, in thicker strata, mixed alternately with quartz 

 and carbonated lime of a decided whiteness. Every thing shows 

 in this singular arrangement, that these various strata have un- 

 dergone a slow or instantaneous pressure at the moment of their 

 formation, and at epochs when these masses still possessed a 

 certain degree of softness. This formation is particularly re- 

 markable at the back of the mountain, the interior of which is 

 mined, and which overhangs the canal the water of which feeds 

 the pumping engines of the wells of St. Barba and St. Agatha. 

 We find it also in the section of the chain against which the 

 furnaces are situated, and in the ravines made by the waters, 

 as well as in many other parts in ascending or descending the 

 Idrixa. 



Banks of. a coarse gres, and a kind of breche almast entirely 

 quartzous, are seen on the road which leads from the church of 

 St. Trinity to that of Calvary; parts are decomposed by their 

 exposure to the air ; others resist its influence, and are not 

 changed by the action of the most violent heat produced by large 

 bellows. Thick strata of an argHo-calcareous schist frequently 

 cover these siliceous masses. 



The manganesiated argil, in which we meet with masses or 

 detached pieces of sulphuretted iron, sometimes crystallized, are 

 often found exposed in certain ravines of these chains, vvhidi the 

 water produced by the melting of the snows seems to have laid 

 bare, 



U a The 



