1866.] MACFARLANE — ON CUPRIFEROUS BEDS. 13 



favor its adoption, and the science of lithology is already well 

 stocked with terms of by no means general adoption, it would 

 seem advisable to retain the word melaphyre to denote such rocks 

 as those above described. With regard to the copper-bearing beds, 

 the fusibility of the rock, and its transition in places into the 

 neighbouring rock connects it distinctly with the melaphyres. 

 This, together with the total absence of crystalline structure, and 

 its apparently detrital character in places, would lead one to sup- 

 pose that these beds are melaphyre tuffs, bearing the same relation 

 to melaphyre, which volcanic tuffs bear to trachytes and basalts. 

 The trap of the Portage Lake District might therefore be pro- 

 perly termed granular melaphyre when it is small-grained and 

 crystalline ; amygdaloidal melaphyre when cavities are present in 

 a crystalline matrix ; compact melaphyre when the rock is fine- 

 grained and crystalline ; and tufaceous melaphyre when the matrix 

 is destitute of crystalline structure. 



The rocks which occur to the eastward of the trap last described, 

 I had no opportunity of examining minutely. They consist pro- 

 bably however of the same rocks as those above mentioned, alter- 

 nating with each other for about one and a quarter miles, which is 

 the distance across the strata from the conglomerate bed of the 

 Albany and Boston property to the so called vein explored by 

 the Isle Roy ale, and other mines. 



About 260 feet west of the ' Isle Hoy ale Vein,' the bed occurs 

 upon which the Grand Portage mine is situated. The colour of 

 the matrix is light-green, thus differing greatly from the beds 

 hitherto described. It has an uneven earthy fracture, is non- 

 crystalline, with small white spots here and there through it. It is 

 fusible and gives water when heated in a glass tube. The amyg- 

 dules are all of a dark-green colour, and frequently consists exclu- 

 sively of delessite. Quite as frequently, however, they consist of 

 that mineral, with a kernel of quartz, or much more seldom of 

 calcspar. The copper is found oftener in the amygdules than in 

 the matrix. As in the other beds larger aggregations of crystal- 

 gave it to black porphyries holding hornblende ; Von Buch and d'Halloy use 

 the name as synonymous with an augite-porphyry, while finally Naumann and 

 Senft restrict the term to rocks which contain neither hornblende nor augite, 

 and are not black in color, as the name melaphyre would imply. Hence I agree 

 with Bernhard Cotta in rejecting the name, while admitting at the same time 

 that some term is requisite to designate the important class of anothosite rocks 

 in which a hydrous mineral (ferruginous chlorite) takes the place of horn- 

 blende or augite.— T. S. H.— (Editor's Notje.) 



