73 



Sample JNo. 42, south of Кар Stewart, contains 9 frag- 

 ments, 1 of which is granite, 3 sediments, and 5 basalts, which 

 is just such an admixture as ллоиЫ be expected when we 

 consider the surrounding formations. 



2. The sandy ingredients in the samples. 



(0-05— 0-5mm.) 



The examination was carried out in the following way: A 

 preparation in Canada balsam was made of each sample; then, 

 by a gradual shifting of the object-glass 100 consecutive grains 

 were counted off. The result is given in the following table. 



The numbers in the above table cannot claim to be abso- 

 lutely exact in detail as it is often very difficult or even im- 

 possible in sand-preparations to distinguish one mineral from 

 another, and several of the different kinds pass into each 

 other. Quartz and felspar are together very easily disting- 

 uished from all other minerals though it is rather difficult to 

 distinguish them from each other. As it would be a quite 

 endless task to find axial images for the individual grains, re- 

 fraction has been chiefly employed in the separation; the grains 

 with a slighter refraction than the Canada balsam are classed 

 under felspar, those with stronger refraction under quartz, and 

 those in which twin-striation or cleavage cannot be seen are 

 probably so small in number in proportion to the quartz and 

 the rest of the felspar, that they can have no appreciable in- 

 fluence on the result. The optically homogeneous felspar is 

 certainly orthoclase in most cases, though a few grains of 

 albite or oligoclase may also enter into this division. 



While the ordinary green hornblende cannot easily be mis- 

 taken for other minerals, augite and olivine are very difficult 

 to distinguish. The augite is almost always of a quite pale 

 violet or brownish-grey colour. The olivine is colourless, or 

 of a quite pale greenish colour. The augite has a somewhat 



