X. PRESIDENT S ADDRESS. 



mile or more deep, and where these have, by the operation of 

 greater pj-essure, been still further thrown over, the amount of 

 dislocation may be imagined. As the mass which has under- 

 gone this process consisted of several series, the parts of which 

 were unconformable to each other, the confusion introduced at 

 the plane where with a little further movement a fault would 

 be produced is somewhat prodigious. Here the rocks are, as 

 it were, rolled out and laminated ; all go alike — gneiss, granite, 

 quartzite, limestone, and an examination, even cursory, of a 

 few slides cut from such specimens impresses upon us the 

 gigantic scale of earth forces more powerfully than, perhaps, 

 even the field phenomena can. The great foldings are always 

 accompanied by smaller folds, and these again by still smaller 

 ones, till a mere waviuess of the rock is the result. On the 

 supposition that pressure is the cause of the metamorphism of 

 rocks, we ought to hud some trace of it here, but Prof. Bonney 

 records that he has found no appearance of changes in that 

 direction ; that there is a certain deposition of quartz cementing 

 the original grains, but these are always more or less easily 

 determinable, and there is no structure approaching that of a 

 true gneiss or crystalline schist. If Dr. Callaway's views turn 

 out to be coirect, and such a careful and learned observer may 

 fairly be trusted till shown to be wrong, we have no hint in 

 the Northern Highlands of the origin of the gneisses, as was 

 the case when the upper series was supposed to be the meta- 

 morphosed equivalent of Silurian shales and grits. This 

 problem still remains to exercise the observation and deductive 

 genius of geologists, and we can only hope for a solution in the 

 future. I venture to think that a hopeful path of enquiry and 

 experiment is opened out by Daubree and others, who have 

 formed minerals by the action of certain substances, Avhich 

 hnally leave little or no trace of their presence in the product, 

 but the intermediary action of which has apparently enabled 

 the silicate to crystallize at a comparatively low temperature. 

 Many of the characteristic accessory constituents of the meta- 

 morphic rocks are among those which have been thus formed 



