4 The Hon. Mr. Strangways on the Geology of Russia. 



admixture of felspar,) and contains many large irregular veins of augite and of 

 hornblende rock*, also the same substances disseminated through its mass in 

 great abundance. Bright purple spots, supposed to be fluor, are common 

 in some varieties ; also moroxite, scapolite, coccolite, and Romantzovite : 

 tourmaline occurs, but rarely. One of the most remarkable minerals of this 

 rock is chondrolite ; it is also one of the most plentiful. It possesses a much 

 greater degree of hardness than the limestone, which is usually washed out of 

 the surface of the weathered blocks, leaving only the yellow or orange-coloured 

 mass of chondrolite behind. By this it appears, that in many cases where the 

 chondrolite is thickly sown in the limestone, the grains, which on the fresh 

 fracture appear to be insulated, do in fact touch one another in some point 

 within, and are sufficiently connected to form a rugged but firm mass. This 

 may be the case also with the other minerals. Chondrolite is found in many 

 other parts of Finland, uniformly in primitive limestone. The pargasite itself 

 has been so long known to mineralogists, and is described in so many peri- 

 odical works, that a particular account of it here would be unnecessary; 

 especially as the Society is in possession of the detailed memoir on pargasite 

 published by Dr. Bonstorff of the university of Abo f. 



The country through which the limestone vein passes is gneiss ; the fissures 

 of which are in a direction parallel to the course of the vein. Sometimes long 

 narrow ridges or plates of gneiss are seen in the body of the limestone itself: 

 these are easily detected, even on the surface, from the difference of colour 

 and superior hardness to the mass in which they are imbedded, which causes 

 them to project considerably above its level. The vein may be traced along 

 the ground, where in many places it serves as a road, by its colour alone : 

 its breadth varies from twenty to a hundred feet, and is quarried in five or six 

 different places. Perhaps it should not, strictly speaking, be termed a vein ; 

 but as it seems to descend perpendicularly, and extends in an unbroken line 

 with little or no change of direction, I adopt the name for want of a better +. 



Passing hence to the main land§, we observe that a gneiss, more or less 



* One of these hornblende veins in one of the quarries near the western extremity of the 

 Island, is represented in Plate I. fig 1. It is singularly interrupted. 



t Dissertatio Chemica, nova experimenta naturam Pargasitce illustrantia proponens. 

 PP. I & II. AboE 1817-1818. This limestone of Pargas, both with respect to itsgeoiogical 

 situation and external character, seems to bear some analogy to that of the Hebrides, especially 

 of the Isle of Tiree. j At Abo it is called a Gang. 



§ Another small island on this coast nearly opposite Bjorneborg is remarkable for rolled blocks 

 of a fine-grained siliceous sandstone, of a yellowish colour, used for polishing glass. It is re- 

 niarkable that a similar stone is found in the environs of Jonkoping in Sweden, especially at 

 Barnarp near the Taberg. 



