182 Proceedings of the Royal Physical Society. 



in Rutley's admirable little book on Mineralogy."^ The fine 

 and extremely useful collection of minerals in the Jermyn 

 Street Museum is arranged upon a plan somewhat similar to 

 that of Mcol ; as is also one of the sections of the Ferguson 

 Collection at Raith, in Fifeshire. The needs of the geologist 

 sometimes lead him to regard minerals more or less with 

 reference to their origin ; which he will probably continue to 

 do, even though our knowledge upon the genesis of many 

 species is as yet in a by no means satisfactory state ; and 

 although it may be very long before there is complete 

 agreement amongst geognosers upon some of the questions 

 connected with the genesis of some few of the species. 



Now that the arrangement of the Collection of Scottish 

 Minerals in the Edinburgh Museum of Science and Art is 

 nearing completion, the time has come when it may be con- 

 venient to review the minerals with special reference to their 

 origin. The Collection contains numerous specimens which 

 yield important information concerning several minerals 

 whose genesis is perhaps even yet imperfectly understood. 

 A review of this kind, even if it serves no other purpose, 

 may at least conduce to further inquiry, and to a critical 

 examination of present and future evidence. 



Scottish minerals may be classified with reference to their 

 origin under two primary categories. The first of these 

 includes all those minerals whose genesis is in any way con- 

 nected with the combined action of cold surface-waters and 

 gravitation, or which have been formed by agencies operating 

 from above downwards. These may be conveniently desig- 

 nated Minerals of Epigene Origin. Practically, all the 

 remainder are due to causes operating from within the 

 earth's crust outwards. In most cases their genesis is con- 

 nected with a high temperature, and with a manifestation of 

 elevatory forces which counteract the effects of gravitation. 

 These will be distinguished as Minerals of Hypogene Origin. 



Presented in a tabular form, these, and their major sub- 

 divisions, may be shown as follows : — 



I. Epigene Minerals. — Those due to changes arising from 

 the joint action of cold surface-waters and gravitation, or 

 ^ Murby's " Science Series." 



