TYPICAL OBJECTS IN NATURAL HISTORY. 125 



No. 1 . As many of the elements as can be exposed under glass. 

 „ 2. Scale of temperatures at which some of the elements appear solid, 



liquid, and gaseous. 

 „ 3. A compound substance, of given weight, exhibited with the rela- 

 tive weights of the ingredients of which it is composed : — 

 Ex. gr. Cinnabar (HgS) ; with sulphur and mercury. 



„ A grain of water (HO); with relative bulks of oxygen 



and hydrogen. 

 „ Gypsum (CaOjSO^ + SHO) ; with lime, sulphuric acid, 



and water. 

 „ 4. Malleability, extreme in gold. 

 „ 5. Ductility, extreme in platina. 

 „ 6. Specific gravity illustrated by a drawing. 



„ 7. Hardness, tested by nine simple minerals adopted in Mohs's scale, 

 each scratched by the one which succeeds, except the last, which 

 is scratched only by diamond. 

 1. Talc. 2. Rock-salt. 3. Calcite. 4. Fluor. ;■». Apatite. 6. Fel- 

 spar. 7. Quartz. 8. Topaz. 9. Corundum. 

 „ 8. Magnetism with polarity, exposed by a compass-needle deflected 



by a piece of magnetite. 

 „ 9. Crystallization produced from four predisposing influences : 



1. Solution, — alum; blue copperas ; and ferrocyanate of potash. 



2. Fusion, — bismuth ; sulphur ; and slag of an iron furnace. 



3. Sublimation, — naphthaline; camphor; and biniodide of mer- 



cury. 



4. Precipitation, — ^lead ; tin; and silver, 

 „ 10. Cleavage, very distinct in, — 



1. one direction, in mica; 



2. three directions, in calcite ; 



3. four directions, in fluor. 



„ 11. Models to illustrate the six systems of crystals; severally repre- 

 sented by a letter and a colour as follows : — 



Cubic system O Red. 



Pyramidal Q Orange. 



Rhombohedral R Yellow. 



Prismatic . P ^ Green. 



Oblique S Blue. 



Anorthic T Purple. 



„ 12. Pseudomorphism in Haytorite, i. e. quartz in the form of datholite. 

 „ 13. Nodular arrangement, 



1. from igneous action,— in devitrified glass; and in Corsican 



granite ; 



2. from aqueous agency, — in iron pyrites ; 



3. raetaraorphic rearrangement,— in a mass of limestone (nodular 



disintegration ) . 

 „ 14. Stalactitic and stalagmitic concretions, — in calcite. 

 „ 15. Polarization of light. 

 „ 16. Double refraction,— in calcite. 



Mineralogi/, 

 An Epitome of this science has been formed by placing one small specimen 

 of every procurable species noticed in Brooke's 'Mineralogy,' on stout card- 

 board of a given size. A letter indicating the system, and printed on the 

 appropriate colour, is pasted on the cardboard to the left above the specimen. 



