82 T. & Hunt on Granitic Bocks. 



ficial magnets, but also to give magnetism to steel needles pre- 

 viously devoid of that property ; but the more recent experi- 

 ments of Riess and Moser* cast such doubt over preceding 

 results that the subject has since received but little attention 

 It is also to be remarked that Faraday, when in Eome with Sir 

 H. Davy in May, 1814, spent several hours at the house of Mor- 

 richini, working with his apparatus and under his directions, but 

 could not succeed in magnetizing a needle. Morrichini attribu- 

 ted the failure to the misty state of the atmosphere. 



With our present imperfect knowledge of the various foms 

 of energy existing in the solar emanation these questions can- 

 not be answered ; but the fact that they can be asked, and the 

 fundamental cosmical relations which will be revealed by their 

 solution, is sufficient to induce men of sicence again to attack 

 this problem,— though its solution baffled all the manipulatire 

 ingenuity and philosophical acumen of a Faradayf— the corre- 

 lation of the solar emanations and electricity and magnetism. 



-Notes on Granitic Rochs ; by T. Sterry Hu>-T, 

 LL.D., F.E.S. First PART.t 



Contexts of Sections.— § 1-2, Definitions of granite and syenite ; §3, 

 of granitic and gneissic rocks; §4-5, Felsiteg and felsite-porpliyi 

 Gneisses and granites of New Englai - "^ " ^ 



™«^ses and granites of New England; § 7, Granitic dyk( 



of granitic veins; § 9-10, Elie de Beaumont on 

 granites and granitic emanations ; §11, Granitic distinguished from concretion- 

 ary veins; § 12, Von Cotta on granitic veins ; §13-14, The author's views oa 

 the concretionary origin of granitic veius ; § 15, The banded structure of gran- 



§ 1. The name of granite is employed to designate a supposed 

 eruptive or exotic unstratified composite rock, granular, crystal- 

 line m texture, and consisting essentially of orthoclase-feldspar 

 and quartz, with an admixture of mica, and frequently of a 

 tnclmic feldspar, either oligoclase or albite. This is the defini- 

 tion of granite given by most writers on lithology, and applies 

 to a great portion of what are commonly called granitic rocks; 

 there are, however, crystalline gTanite-like aggregates in which 

 the mica is replaced by a dark colored hornblende or amphihoe, 

 and to such a compound rock many authors have given tlie 

 name of syenite, while to those in which mica and hornblende 

 co-exist, the name of syenitic granite is applied. It is observed 



