1 6 Macfarlane on the Primitive Formations 



nymous with the reticulated gneiss. In corroboration of this I take 

 the liberty of quoting the following remarks of Sir William 

 Logan: — " In the Reports of the Survey, the Laurentian rocks 

 have been described in general terms, as gneiss, interstratified 

 with important masses of crystalline limestone. The term 

 gneiss, strictly defined, signifies a granite with its elements, 

 quartz, feldspar and mica, arranged in parallel planes, and con- 

 taining a larger amount of mica than ordinary granite pos- 

 sesses, giving to the rock a schistose or lamellar structure. 

 "When hornblende, instead of mica, is associated with quartz and 

 feldspar, the rock is termed syenite, but as there is no distinct 

 specific single name for a rock containing these elements in a 

 lamellar arrangement, it receives the appellation of syenitic 

 gneiss. Gneiss rock then becomes divided into two kinds, 

 granitic and syenitic gneiss, and the word gneiss would thus ap- 

 pear rather to indicate the lamellar arrangement than the min- 

 eral composition. Granitic and syenitic gneiss were the terms 

 applied to these rocks in the first Reports ; but as granite and 

 syenite are considered rocks of igneous origin, and the epithets 

 derived from them might be supposed to have a theoretical re- 

 ference to such an origin of the gneiss, while at the same time 

 it appears to me that the Laurentian series are altered sedimen- 

 tary rocks, the epithets micaceous and hornblendic, have been 

 given to the gneiss in later Reports, as the- best mode of de- 

 signating the mineral composition and lamellar arrrangement, 

 without any reference whatever to the supposed origin of the 

 rocks. (Report 1853-56, pp. 49 and 50.) 



Further " The space between them (the bands of limestone) 

 is occupied by gneiss, the banded structure of which is vis- 

 ible in a vast number of places, but a large part of the rock is 

 coarse grained ; the feldspar being in individuals, frequently at- 

 taining an inch and sometimes more in diameter, while the mica- 

 and the quartz, often accompanied by hornblende, and the former 

 sometimes replaced by it, are distributed among the feldspar in 

 such a manner as to give a reticulated aspect to the surface. 

 Beds of this character are sometimes thin, but when thick and 

 massive, which they usually are, they might upon a first inspec- 

 tion be mistaken for igneous instead of altered rocks. Upon a 

 careful study of the case, however, it will be perceived that this 

 reticulated structure is accompanied by an obscure arrangement 

 of the meshes of the net-work, into parallel lines, which are found 



