98 SCIENCE PROGRESS. 



i. Precambrian Rocks. 



In dealing with these rocks, it is really the province of 

 the stratigraphical geologist to treat of such as are known 

 to be " stratified " and to leave the still mysterious " schists " 

 alone, but in these days, when the latter rocks have so 

 fascinated the minds of geologists, it is a hard task to pass 

 them by. Perhaps, in the present state of our knowledge, 

 it will be the best plan to point out what work has been 

 done in each British area where rocks have been claimed as 

 Precambrian, alluding only briefly to those regions where 

 the age of the rocks has not been pretty clearly established. 

 In doing so, we must pass along the length of the island 

 from Cornwall to Ross, and may commence in the south, 

 and travel northward, starting with the Lizard district. 

 Awaiting with confidence for palaiontological evidence con- 

 cerning the age of these and other doubtful Cornish rocks, 

 we pause for a moment only to refer to a paper which is 

 rather petrographical than stratigraphical (i), in which the 

 writer notices the existence of ultrabasic, basic, intermediate 

 and acid intrusive igneous rocks, and argues in favour of 

 their differentiation from an igneous magma. Travelling 

 north from thence, we reach a spot where there is more 

 satisfactory evidence of the Precambrian age of the rocks, 

 for the Cambrian rocks are found in their immediate 

 vicinity. This is the Malvern ridge. Here the publica- 

 tions of the six months under consideration deal with petro- 

 graphical matter also, and a reference to the Geological Maga- 

 zine (2) will enable the student of Archaean rocks to see 

 two sides of a question as to the origin of certain biotites 

 in the crystalline rocks of this ridge. Concerning the 

 Scotch rocks Mr. Barrow has a paper (3), which to a large 

 extent summarises work and views advanced in detail in a 

 former paper which he read before the Geological Society, 

 and a very acceptable contribution to our knowledge of 

 the Precambrian rocks comes in the shape of the geological 

 survey map of the district around Gairloch (4), so long cele- 

 brated on account of the relationship between the Torridon 

 sandstone and the gneissose rocks in that region. Of the 



