451 



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 • 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, 

 and by pointing out with equal fidelity all those districts which come 

 within the application of his theory, as well as those great metal- 

 liferous tracts, in which as yet no trace of contiguous, unstratified 

 rock has been observed. Why are we to shrink from the supposition, 

 that in this, as in the production of other phsenomena, nature may 

 not have employed various means, when it is known that a distin- 

 guished French chemist*, imitating her energies, has succeeded in 

 producing simple minerals by the direct union of their constituents. 

 If, therefore, the ingenuity of a second Hall should demonstrate the 

 very manner in which volcanic forces, under great pressure, may 

 have produced effects analogous to those of sublimation beneath 

 the common atmosphere, there are still wide fields for experiment. 

 For who can venture to expound all the possible effects of those 



* Berthier. 



