450 Intelligence and Miscellaneous Articles. 



with rounded stones pushed up by floe-ice, with solid rock beneath 

 glaciated by the floe-ice. Several minor phenomena connected with 

 the glacial geology of JNovaya Zemlya are also described. The 

 raised beaches of Franz Josef Land are noticed, and immense 

 deposits occurring in Spitsbergen, which were originally formed 

 under water in front of glaciers, alluded to. These, as well as other 

 submarine deposits of glacio-marine origin seen elsewhere by the 

 author, show no signs of stratification. 



Prof. Bonney describes specimens brought by Col. Feilden from 

 Norway, the Kola Peninsula, and Novaya Zemlya. Prom an 

 examination of the rocks obtained in situ in the latter region, 

 Prof. Bonney confirms Col. Peilden's suggestion that the Kolguev 

 erratics may have come from Novaya Zemlya. 



2. ' Extrusive and Intrusive Igneous Rocks as Products of 

 Magmatic Differentiation.' By Prof. J. P. Iddings, For.Corr.GKS. 



The author, after pointing out the propositions concerning 

 differentiation of magmas upon which he is in agreement with 

 Prof. Brogger, discusses the points of difference, and describes the 

 relation of the igneous rocks at Electric Peak to all of those which 

 took part in the great series of eruptions which occupied almost the 

 whole Teitiary period, and spread themselves over a vast territory 

 in Montana, Wyoming, and Idaho. In Tertiary times the eruptions 

 were at first largely explosive, and the accumulation of tuff-breccia 

 formed a chain of lofty volcanoes, comparable with the Andes in 

 size as well as in the nature of their material (andesite and andesitic 

 basalt). After considerable erosion of these volcanoes, gigantic 

 fissure-eruptions flooded the region west of the denuded volcanoes. 

 The massive lava-streams which welled from these fissures consisted 

 at first of rhyolite with an average silica-percentage of about 74, 

 alternating occasionally with basalt; but the great bulk of the 

 basalt was poured out immediately after the rhyolite from fissures 

 still farther to the west and south-west. In the case of these 

 extrusive rocks, whose volumes are of such magnitude, the evidence 

 drawn from the succession of their eruptions and from their com- 

 position is of a higher order than that derived from the smaller and 

 more localized eruptions, and it is upon evidence of this order that 

 the author ventured to enunciate the principle that in a region of 

 eruptive activity the succession of eruptions in general commences 

 with magmas representing a mean composition and ends with those 

 of extreme composition. 



XLYI. Intelligence and Miscellaneous Articles. 



CARBON MEGOHMS FOR HIGH VOLTAGES. BY W. M. MORDEY*. 



^HE insulation of apparatus and cables used with high voltages 

 ■*- should be tested with high voltages. For this and many other 

 purposes some inexpensive and trustworthy form of high resistance 



* Paper read before Section A, British Association, Liverpool, Sep- 

 tember 23rd ; 1896. Communicated by the Author. 



