On the table are specimens of syenites of the different schools, and it will be at once apparent how much they differ; it will also be observed how nearly the one approaches a granite, and the other a diorite. To compare the definitions of Lyell, Dana, and others;— Lyell and Dana. Syenite resembles a granite in which the mica is replaced by hornblende, also that the felspar may be orthoclase or oligoclase; this is, therefore, eminently acidic, but the acidic character is not constant or characteristic. Cotta, on the other hand, says that syenite consists of orthoclase or microlene and hornblende, which may have mica and quartz as accessories, but if either of these are abundant it at once becomes syenitic granite or syenitic gneiss—the difference is more apparent by comparison with diorite and granite. Syenite. Dana:—Felspar, quartz, hornblende. Cotta:—Orthoclase, hornblende. Granite. Dana:—Felspar, quartz, mica. Cotta:—Felspar, quartz, mica. Diorite. Dana:—Felspar and hornblende Triclinic. Cotta:—Felspar and hornblende Triclinic. From the above it will be at once apparent that the German classification is not practical, i. e., it cannot be used in the field, for it is rather too much to expect that a geologist, with only an acid bottle, pocket lens, and knife, can decide with any degree of certainty on the angles a half-embedded crystal makes, or the system it belongs to; for although orthoclase is monoclinic and oligoclase triclinic, still the angles are very nearly the same, (albite) 118°a or 120°o 86°a or 90°o etc., etc. The inconvenience of this classification is well shown by the fact that Werner, who first proposed it to suit a certain rock, subsequently called the same rock a diorite. If, however, the English system is adopted, there can be no hesitation in at once determining the quartz, felspar, and hornblende; felspar and hornblende come in as hornblende rock if the felspar is decidedly triclinic, if not, as a diorite. The English school, or rather the American branch of it, has many claims to preference over all others, chiefly on account of its simplicity, and this simplicity is insured for some time to come, as the Americans have so much room for real practical science, and cannot afford to waste time and talents in multiplying names and then finding out some compound to suit them; the old proverb about a certain personage finding mischief for idle hands, applies to the natural sciences as well as anything else, for when a certain point has been