science, than the perusal of this commonly supposed old-fashioned and antiquated “Principia” of speculative science. We will now say a few words on the great chemical truths which the “Principia” revealed. In 1734, not a whisper had been breathed regarding the composite nature of the atmosphere. The earliest date which can be assigned for the practical discovery of the two-fold nature of atmospheric air, is 1772-4, the date of Priestley’s celebrated experiments. But we find in the “Principia,” that Swedenborg sets forth the following facts:—that pure and dry atmospheric air is a compound of two constituents; that these constituents are combined in unequal proportions; that the element greatest in quantity is the extinguisher of combustion; and lastly, that the element greatest in quantity is a constituent of water as well as of air. The merest tyro in science will, at a glance, perceive the importance and extent of ground which these propositions cover, and how profound must have been that genius, which, in the midst of the deepest scientific darkness, could draw from nature these deep and choice truths. But this was not all. Water as well as air yielded to him the secret of its constitution. In Swedenborg’s day, the whole world thought and spoke of water as an element, and even after the composite nature of air was revealed, water maintained its elemental character up to 1783, when the discovery was almost simultaneously made by Watt, Priestley, Cavendish, and Lavoisier, that water, like air, is a result of the combination of two gases. Now in the “Principia,” written fifty years before, we are expressly told that pure water is a compound substance, and the particulars and quantities of the two elements in its composition are correctly given. There are many other truths in modern science which the “Principia” anticipates; such as the atomic theory, and the identity of electricity and lightning; but we must draw to a close. Enough has been said to show the high merits of the book, and to prove how worthy it is of the study and attention of all true lovers of science. The publication of the “Principia” gained for its author great reputation, and his friendship and correspondence were eagerly courted by all the philosophers of his day. In December, 1734, the Academy of Sciences at St. Petersburg appointed him one of their corresponding members. The Pope honored the work by placing it in that noble catalogue of books, the Index Expurgatorius, in 1739.