

Intelligence and Miscellaneous Articles. 313 



differentiation from an originally homogeneous magma. Corre- 

 sponding to the two types of rock are two forms of variolite. 

 These are fully described, and their mode of development is dis- 

 cussed. 



The variolites occur near Aberdaron and at places along the coast. 

 Their spherulitic structure often is developed towards the exterior 

 of contraction-spheroids, and in this and in other particulars they 

 correspond with those of the Fichtelgebirge and of the Durance. 

 The volcanic rocks include lava-flows and fragmental masses, both 

 fine ash and coarse agglomerate. They are associated with lime- 

 stones, quartzose, and other rocks, which are possibly sedimentary, 

 but which give no trustworthy evidence of the age of the variolites. 



2. " On the Petrography of the Island of Capraja." By Hamilton 

 Emmons, Esq. 



The rocks of Capraja consist generally of andesitic outflows resting 

 on andesitic breccias and conglomerates. The southern end seems 

 to have formed a distinct centre of volcanic activity, whose products 

 are younger in age and more basic in character than the rocks of the 

 rest of the island, and may be termed ' anamesites.' The lavas 

 appear to have flowed from a vent at some distance from the cone 

 which probably occurred here and gave out highly scoriaceous 

 fragments. In the other parts of the island andesite is almost 

 everywhere found, with patches of the underlying breccias here 

 and there in the valley bottoms. The chief centre of activity prob- 

 ably lay west of the centre of the island. 



Petrographical details of the andesites and anamesites, descrip- 

 tions of the grouudmass and included minerals of each, and chemical 

 analyses are given. As regards the age of the constituents, the 

 author arranges them in the following order, commencing with the 

 oldest : — magnetite, olivine, augite, mica, felspar, nepheline. 



XXXI. Intelligence and Miscellaneous Articles. 



ON A NEW ELECTRICAL FURNACE. BY M. HENRI MOISSAN. 



THIS new furnace is made of two carefully plane pieces of quick- 

 lime one placed under the other. In the lower one is a longi- 

 tudinal groove for the two electrodes, and in the middle is a small 

 cavity more or less deep acting as a crucible ; it contains a layer 

 of a few centimetres of the substance to be acted upon by the arc. 

 A small carbon crucible may also be placed in it containing the 

 substance to be calcined. In the reduction of oxides and the 

 fusion of metals, larger crucibles are used, and through a cylin- 

 drical aperture in the upper brick small cartridges of the compressed 

 oxide and carbon can from time to time be added. The diameter 

 of the carbons which act as conductors w T ill of course vary with the 

 strength of the current; after each experiment the end of the 

 carbon is changed into graphite. 



The current most frequently used was one of 30 amperes and 

 Phil. Mag. S. 5. Vol. 35. No. 214. March 1893. Y 



