168 THE MICROSCOPE. Nov. 



all round. Similar felspars have been seen in almost all 

 specimens of the sands examined from Newton upwards. 



There is also some evidence to show that quartz grains 

 from the granite twenty miles up the Nairn, are also to 

 be found among the grains of the upper members of the 

 series. These consist of grains made up as it were of 

 many smaller quartz crystals seemingly dovetailed to- 

 gether. They produce a peculiar etfect when examined 

 with polarized light ; and the grains in the granite and 

 the sandstones have this effect in common. Such grains 

 are also to be found in some of the other granites, but 

 these are the most typical, and correspond most closely 

 to the grains in the sandstones. 



It should be stated, that when sand grains are built 

 up into sandstones, secondary quartz is apt to be depos- 

 ited around the sand grains by water containing silica in 

 solution percolating through the beds, and depositing it 

 between the original grains. When we come to exam- 

 ine the grains after separation for the purpose of analy- 

 sis, they often have clear bands of this secondary quartz 

 around them (figure 7). But when we have discounted 

 all this secondary quartz in the Spynie sandstones, there 

 are many grains that do not differ widely from regular 

 mathematical forms. Now such grains do not occur in 

 granite, they do not occur in gneiss. The only rock I 

 know that shows such grains is quartz-felsite^ — which is 

 nowhere, so far as I know, found in situ in this locality 

 now, but is common in two varieties among the pebbles 

 on the shore at Lossiemouth. 



[We quote the foregoing, which will prove ol" the greatest interest to our 

 readers, from a pamphlet Entitled "Sand Grains," which is for sale by Alex- 

 ander Watt. 144 High Street, Elgin, England, to whom we advise our read- 

 ers to apply for the entire treatise of 32 pages. Enclose 30 cents to him in 

 the form of an International Money (Jrder. — Editor]. 



