_seleniet_ an alkaline compound in which selenium acts the part of a supporter or electro-negative body. The same mode of naming might and doubtless will be extended to all the other similar compounds, as soon as it becomes necessary. In order to form a systematic nomenclature it will speedily be requisite to new-model all the old names which denote acids and bases; because unless this is done the names will become too numerous to be remembered. At present we denote the alkaline bodies formed by the union of _manganese_ and oxygen by the name of _oxides of manganese_, and the acid compound of oxygen and the same metal by the name of _manganesic acid_. The word _oxide_ applies to every compound of a base and oxygen, whether neutral or alkaline; but when the compound has acid qualities this is denoted by adding the syllable _ic_ to the name of the base. This mode of naming answered tolerably well as long as the acids and alkalies were all combinations of oxygen with a base; but now that we know the existence of eight or ten classes of acids and alkalies, consisting of as many supporters, or acidifiable bases united to bases, it is needless to remark how very defective it has become. But this is not the place to dwell longer upon such a subject. The alkalifiable bases are thirty-one in number; namely, potassium, sodium, lithium, barium, strontium, calcium, magnesium, aluminum, glucinum, yttrium, cerium, zirconium, thorium, iron, manganese, nickel, cobalt, zinc, cadmium, lead, tin, bismuth, copper, mercury, silver, gold, platinum, palladium, rhodium, iridium, osmium. The compounds which these bodies form with oxygen, and the other supporters, constitute all the alkaline bases or the substances capable of neutralizing the acids. Some of the acidifiable bases, when united to a certain portion of oxygen, constitute, not acids, but _bases_ or _alkalies_. Thus the _green oxides of chromium and uranium_ are alkalies; while, on the other hand, there is a compound of oxygen and manganese which possesses acid properties. In such cases it is always the compound containing the least oxygen which is an alkali, and that containing the most oxygen that is an acid. The opinion at present universally adopted by chemists is, that the ultimate particles of bodies consist of _atoms_, incapable of further division; and these atoms are of a size almost infinitely small. It can be demonstrated that the size of an atom of _lead_ does not amount to so much as 1/888,492,000,000,000 of a cubic inch.