354 Minerals. 



The following collections are auxiliary to the Systematic 

 Collection : 



la. A series of Isolated Crystals and Models of Crystals, 

 illustrative of crystalline form ; part is exhibited in two 

 wall-cases (D, E) of the Gallery. 



16. A series of Slices of Crystals prepared for examination 

 by transmitted polarised light; they are preserved in 

 the drawers of a special cabinet. 



Some of the crystals and slices of crystals are those of 

 native products (minerals) ; others are those of illustrative 

 products in the formation of which human action has 

 intervened, and which are therefore generally called 

 "artificial." 



2. A collection of Pseudomorphs ; the best and most instruc- 



tive specimens are exhibited in three table-cases (44, 45, 

 46) in the Pavilion ; the remaining specimens are in the 

 drawers of those cases. 



3. A series of specimens illustrative of the Forms of Silica, 



arranged and described in 1884 by Professor John 

 lluskin ; exhibited in table-case 47 in the Pavilion. 



4. A collection of Enclosures, illustrating the enclosure of 



one mineral by another ; exhibited in a portion of table- 

 case 42 in the Gallery. 



5. A small set of so-called " Artificial Products " identical in 



their essential characters with, or closely allied to, recog- 

 nised mineral species ; some are exhibited in a portion 

 of table-case 42 in the Gallery. 



6. A collection of polished slabs of Ornamental Stones ; 



exhibited in a wall-case (A) of the Corridor, near the 

 entrance to the Gallery. 



7. The most interesting of the Recent Accessions are kept 



together for a time, and before being incorporated with 

 the Collection are exhibited in table-case 43 in the 

 Gallery. 



It may be added that mineral species are defined, not by 

 means of type-specimens, but by means of numerical quantities 

 which specify the crystalline form and chemical composition of 

 the substance; figures of actual mineral specimens have thus 

 little or no classificatory value and are rarely published. 



