46 Geological Society. 



the Ordnance surveyors j chiefly, I believe, through the intervention 

 of Capt. Portlock, R.E. 



The Archdeacon shows that this region has for its mineralogical 

 axis a mountainous range of mica schist, and other primary rocks, 

 the overlying deposits consisting of partial conglomerates, succeeded 

 by the carboniferous limestone and unproductive coal measures, — the 

 former containing, as in many parts of England, a lower limestone 

 shale and an oolitic limestone. In describing the rocks of intrusive 

 character, this author is to be much commended for having traced, 

 with precision, the course of no less than eleven basaltic dykes, within 

 a zone of eleven miles in breadth 5 which are parallel to each other, 

 trending nearly W. to E., and striking through all the rocks of the di- 

 strict — one of them being observable for the distance of 60 to 70 

 miles. 



With such works as these before us, we may feel assured that the 

 day is not far distant, when a manual of the structure of the whole 

 of our sister kingdom may be compiled. This useful work will doubt- 

 less be achieved by the efforts of the members of the new Geological 

 Society of Ireland, who in the mean time will, it is hoped, extend 

 their discoveries to Galway, and such tracts as have not been ex- 

 amined by Weaver, Griffiths, and other good observers. 



Rocks of Igneous Origin. — Two of our Foreign Members have, 

 in the past year, favoured us with communications, both of which 

 relate to igneous action. 



Signor Monticelli, of Naples, has noticed, in one of the largest and 

 most ancient currents of Vesuvius, called La Scala, that besides the 

 appearances of regular stratification which the lava possesses, as for- 

 merly observed by Breislac, it presents, when still more deeply cut 

 into, a curvilinear arrangement, proving that these masses have been 

 formed in concentric layers around an elliptical nucleus. 



Professor Necker of Geneva, reviving and extending an ingenious 

 hypothesis of Dr. Boue, has led the way in attempting to bring under 

 a general law the relation of metalliferous veins and deposits to those 

 crystalline rocks which, by the great majority of modern geologists, 

 are considered to have been produced by fire. 



Humboldt had indeed already expressed his belief that the mines 

 on the flanks of the Oural, being associated with porphyritic and 

 granitoid rocks, have resulted from former volcanic agency 5 and 

 Professor Necker now cites many additional authorities, to show si- 

 milar juxta-positions in other parts of the world. Whether the doc- 

 trine of sublimation, suggested by the author as the best explanation 

 of this problem, can be sustained, is very doubtful; since the case 

 which first led him to a contemplation of these general views, — a 

 deposition of specular iron on the surface of a stream of Vesuvian 

 lava, is one which, having taken place under the terrestrial atmo- 

 sphere, may have been due to a cause which could scarcely have 

 been co-existent with submarine or deeply-seated subterranean phse- 

 nomena. Such difficulties, however, instead of checking, ought rather 

 to stimulate us to pursue with vigour this animating train of inquiry, 

 by gathering together data responding to the queries of M. Necker, 



