588 MINERALOGY what casual juxtapositions brought about by the present system of arrangement, we find different compounds, such as sulphates and carbonates, crystallized in different forms; while a species which is a compound of both these, a sulphato-carbonate, has the general form of the sulphates. From this fact it is concluded that sulphur has a more energetic formative power than carbon. An excellent and simple example of the principles on which mineral types and groups are arranged will be found in Dana's "Mineralogy," fifth edition, p. 34, under the head of " Sulphides." Nomen- clature. Mineralogists have chosen the ter- mination ite to characterize the names of their species. Itis or itea was used by the Greeks and Romans for this purpose, and it was ap- pended to some word signifying a quality, lo- cality, or some other fact relating to the min- eral. Haematites, for instance, referred to the red color of the powder, and syenites took its name from Syene in Egypt. Werner, in the last century, introduced the custom of naming minerals after persons, and, though much op- posed for years, especially by French mineral- ogists, this is now the common usage. Its popularity does not spring so much from the desire to do honor to discoverers and distin- guished men, as from the liability to error when an attempt is made to name a mineral from some supposed quality while the infor- mation about it is still imperfect. Many other terminations are in use, as ine, ane, ene, ase, age, ome, ote, &c. ; but these have come down to us from former years. At present the rule is to use the termination ite, or if another is employed the latter must be applied to all minerals of the same class. A great advance in uniformity has been made by Dana, who undertook a thorough collation of the litera- ture of the science, and applied the law of priority wherever it could be done without injury, thus restoring many old names. While ite is used for minerals, yte is used for rock 'masses, which, to deserve the application of the word, should consist principally or entire- ly of the compact mineral. Thus doleryte and pyroxenyte are massive deposits of the minerals dolerite and pyroxene. Mineralology is the name given to the study of the laws which govern the formation of minerals. While the chemist constantly endeavors to work with pure materials and to have but few elements present in the artificial production of mineral compounds, nature has undoubtedly formed many or all of the mineral species from sources in which a great number of elements were mixed. The circumstances under which these elements were brought together, their proportion, and the influences to which they were individually or collectively subjected af- terward, must have varied within very wide limits ; and the fact that definite and unvarying species have been produced from heterogene- ous compounds is proof of the operation of fixed and probably simple laws. On the other hand, the slight differences which are notice- able in the characteristic marks of a great many species are probably the traces of the different conditions under which the individu- als of the species were formed. The develop- ment of these laws, and of the forces which have modified them, forms the speculative part of mineralogical science, and makes the science itself an important factor both in the history of the earth and in the development of chemical knowledge. The present state of this knowledge will not permit a trustworthy state- ment of mineralological facts within the limits of this article. It is sufficient to point out some of the modes in which compounds may be formed. These are : 1, union of two gase- ous elements ; 2, union of one gaseous and one fluid or solid element ; 3, union of two fluids ; 4, union of one fluid and one solid ; 5, combi- nations at a high temperature (igneous fluidity forming a matrix from which species separate on cooling) ; 6, combinations at a low tempera- ture. Artificial Minerals. By imitating these and other processes, many of the characteristic species may be reproduced, and the combina- tions always show themselves to be governed by the same laws that are discernible in the formation of true minerals. These artificial minerals mostly result from three sources : the study of chemical laws by experimental pro- cesses, the desire to produce gems by artificial means, and the casual formation of definite min- eral compounds in metallurgical work. Of the salts which result from chemical reactions, a great number have been found in nature. Of minerals used as gems, the ruby, aquamarine, garnet, topaz, spinel, chrysoberyl, apatite, and others have been produced, but not of a size large enough to make them useful as orna- ments or their manufacture profitable. Met- allurgical processes, where high temperatures and the action of gaseous substances are long continued, and where compounds of all degrees of fusibility are melted and chemically com- bined, are a fruitful source of artificial and very perfect minerals. A few furnace products have never been found in nature. While arti- ficial minerals are apt to be less perfectly crys- tallized than the native specimens, they are also apt to be of simpler forms, and have sometimes served to determine the primitive angle when it could not be decided by natural specimens. Historical. While the ancients were acquainted with a great number of min- erals, and observed the existence of crystals and the importance of physical characters, their complete ignorance of all our modes of investigation prevented their obtaining any real knowledge of the distinctive species. Stones of the most diverse composition, some minerals and some rocks, were grouped undei one name, and it is frequently impossible to recognize from their description the minerals they knew. Theophrastus (315 B. C.) was the earliest writer on the subject, though other authors frequently referred to minerals as rem-
