86 NATURAL SCIENCE. August. 



garnet, magnetite, and perhaps quartz. The garnet often streams 

 out in rays from a centre, forming micropegmatitic intergrowths with 

 other minerals, after the manner of the spheruHtic groupings in many 

 eurites or fine-grained granites. 



In the diorites of Chota Nagpore and the Sonthal Pergunnahs in 

 Bengal, and in a series of masses from the hills of the Madras Presi- 

 dency, ranging from granites to peridotites, Mr. Holland has studied 

 the development of garnets by interaction among the original con- 

 stituents. Where the garnet lies against pyroxene, or against the 

 hornblende which is paramorphically derived from pyroxene, a 

 reaction-border is visible in microscopic sections ; moreover, the 

 garnet bulges out towards the adjacent pyroxene, filling curved 

 recesses in the latter, as if it had arisen at the expense of its neighbour. 

 The stages seem to be as follows : the pyroxene becomes schillerised ; 

 then follows the formation of a zone of hornblende, which passes into 

 a reaction-border, resembling the mingled materials known as " kely- 

 phite " ; and finally, according to the author, true garnet appears. 

 The field-relations of the more pyroxenic and the more garnetiferous 

 masses support the view that the latter are metamorphosed varieties 

 of the former, the granular (" granulitic ") structure having arisen from 

 dynamic changes. Mr. Holland observes a fact commonly noticeable 

 in our European " pyroxene-granulites " — the colour of the garnet 

 and the pink tint of the pleochroism of the hypersthene are closely 

 similar in the same rock-section ; and he urges that this is due to a 

 significant similarity in chemical composition. Anon he grows bolder, 

 and regards the micropegmatitic intergrowths of felspar and garnet 

 as of secondary origin, the felspar itself being " a by-product in the 

 decomposition of the pyroxene." 



We fancy that Mr. Holland accepts too unhesitatingly the theory 

 of the secondary origin of the similar intergrowths of quartz and 

 felspar, such as are common in the so-called " granophyres " of 

 Rosenbusch. Nor is the analogy a safe one, for surely micropegma- 

 titic structure must be regarded as primary in a still wider range of 

 igneous rocks, equally with the pegmatitic structure of so many 

 igneous veins. The value of the present paper lies in its attempt to 

 connect the phenomena of a large series of rocks ; and the force of 

 its arguments will at any rate compel us to study again, especially in 

 their field relations, the " pyroxene granulites " of more familiar 

 areas. 



The Sight of Children. 



Mr. Brudenell Carter has recently presented to " My Lords " 

 of the Committee of the Council for Education a valuable report upon 

 the vision of elementary school children in London. Children to the 

 number of 8,125, in twenty-five schools, were first submitted by their 

 teachers, according to his directions, to the simpler test of vision. 



