The difficulty of devising a natural classification of minerals has been recognized by most mineralogical writers, and up to the present time no very satisfactory arrangement has been generally adopted. In the classification of the animal and vegetable kingdoms, although the systems have greatly varied from time to time, something like uniformity has pretty generally existed ever since Linnaeus proposed his famous system of double nomenclature ; but in mineralogy every writer does that which is right in his own eyes—not because there is no king—but because they are many and mutually antagonistic.