these genera are poisonous ;-4th order, BATRACHIA, consisting of seven genera, as typified in the Toad, Frog, &c., fossil remains of which have been abundantly found of a gigantic size.

The fourth class (PISCES, or FISHES) are vertebrated animals, with cold red blood, respiring by branchiæ, or gills, and moving in the water by the aid of fins. A knowledge of their form and habits is scientifically called ICHTHYOLOGY.-Cuvier divides this class into two sub-classes-the cartilaginous and the osseous-which he distributes into nine orders, three being in the former sub-class, and six in the latter.

Invertebrate animals are divided into MOLLUSCA, ARTICULATA, and RADIATA. The Mollusca is so called from the body being soft and molluscous. It is divided into four classes, the Mollusca, Conchifera, Tunicata, and Cirripeda. The first class is subdivided into five orders, founded on the organs of locomotion. The second, third, and fourth classes, the Conchifera, the Tunicata, and the Cirripeda, are each divided into two orders. The shell of the fourth class is always multivalve, or composed of a number of separate pieces.

The next great divisions of invertebrated animals are the Articulata and the Radiata, which are each divided into five classes. The fifth class of invertebrates are the Annelides, or Worms; the sixth class, the Crustacea, which respire by branchiæ, or branchial lamine; the seventh class, the Arachnides, or Spiders; the eighth class, the Myriapoda; and the ninth class, the Insecta, or Insects a knowledge of their forms, habits, &c., being termed ENTOMO

LOGY.

Entomology has been subdivided into eleven orders, viz., Thyanoura, apterous or wingless insects;-Parasita, so called from living on other animals ;Siphoniptera, which have mouths with a sucker of two pieces;-Coleoptera, or insects with four wings, the upper ones in the form of cases, as the Beetle, the Lady-bird, &c. ;-Orthoptera, with elytra coriaceous, as the Earwig, Cockroach, &c.;-Hemiptera, with two wings covered, and an elytra, as in the Grasshopper;-Neuroptera, with four naked, reticulated, transparent wings, as the Dragon-fly;-Hymenoptera, with four naked, veined wings of unequal size, with a sting at the anus, as the Bee, Wasp, Gall-fly, &c.;-Lepidoptera, with four membranaceous wings, covered with farina, as the Moth and the Butterfly; -Strepsiptera, with two naked, membranous wings longitudinally folded ;Diptera, with six feet, and two membranous, extended wings, as the Gnat, Horse-fly, &c.-Insects generally exist in four states; first as an egg, next as a worm, or larva, then a chrysalis; in which state it remains dormant for a certain term, when in due time it becomes a moth, a beetle, or other insect with wings, in which state it propagates its species and dies. Some insects envelop themselves in a fine web previously to entering into their chrysalis state, of which the silkworm is a beautiful exemplification.

To enumerate the species, or even genera, of the animal kingdom, and define them in a portable Dictionary like the present one, would be an impossibility. Hence the Editor has chiefly confined himself to Classes, Orders, Families, Tribes, &c., of animated nature, briefly adverting to the genus or species of any class or order when of more than usual importance. The following table, however, presents an approximate estimate, according to Swainson, of the number of species of animals existing on the surface of the earth:

Next to Zoology is the science of Vegetation, called BOTANY, which consists of a knowledge of plants, their several kinds, uses, and virtues. The principal writers on this interesting science are Linnæus and Jussieu. The Linnæan System of classification is founded on the fact that there is in vegetables, as well as in animals, a real distinction of sexes, and that each plant may be analyzed by its several organs of fructification, which consist of the calyx, or flower-cup; the corolla, or blossom; the stamen; the pistillum; the pericarpium, or seed-vessel; and the semen, or seed. Thus the vegetable kingdom was divided by this great naturalist into twenty-four classes, of which twenty-three belong to the flowering and one to the flowerless plants. These, again, are subdivided into orders, the orders into genera, these again into species, and many of these into varieties. The names of the classes and orders are of Greek derivation, and allude to the functions of the respective organs. The first eleven classes are distinguished entirely by the number of stamens, which are called Monandria, Diandria, Triandria, &c., as far as Dodecandria, from the Greek words one, two, three, &c., combined with male (andria), because the stamens of flowers are compared to males, and the pistils to females. Hence the orders are denominated Monogynia, Digynia, &c., to Polygynia, according as the flower has one or more pistils; so called from the Greek monos one, and gyne a female. Thus in the third class (Triandria) are found most of the natural order of Grasses.

The Natural System of plants, as devised by Jussieu, differs materially from the Linnean system; for it takes into consideration the entire organization and form of the plant, with its peculiar habits; and the most striking genus of a tribe of plants gives name to the order; as, for instance, the Rose forms the type of the natural order Rosacea, and the Violet that of the order Violacea; these orders being each described under their respective heads in this Dictionary. In the same manner Jussieu divided the entire vegetable kingdom into classes, orders, and genera. These classes have no appropriate names, but are distinguished by numbers, with a short definition of the essential character of each. The orders are chiefly named, as just stated, after some principal genus belonging to each. Thus the order Campanulaceæ derives its name from Campanula (the Canterbury Bell), which is a diminutive of the Latin campana a bell; the genus having been so called from the resemblance of its corolla to a bell.

A third system in the classification of the vegetable kingdom is the one devised by our distinguished countryman, Professor Lindley, which is based upon the most accurate and extensive information, and which, in the botanical teaching of our schools, appears in some measure to be supplanting the recognised systems of Linnæus and Jussieu. Dr. Lindley reduces the whole of the vegetable creation to two great divisions, the "Asexual, or Flowerless Plants," and the " Sexual, or Flowering Plants; " and these he subdivides into seven distinct classes; two of them under the Asexual plants, as the Thallogens and the Acrogens, and the other five under the Sexual, as the Rhizogens, the Endogens, the Dictyogens, the Gymnogens, and the Exogens-this last class being composed of innumerable races.

Such are the principal systems of botanical classification (says the Editor of the supplementary volume to the "National Cyclopædia") which have been presented to the world; and although there have appeared, at different times, about thirty systems, "it is still probable," says Dr. Smith, "that the best one, at the present moment, is so imperfect that it must be amended yearly."

We now enter upon the third grand division in physical science, called MINERALOGY, in which we learn the form, nature, and uses of inorganic matter; so denominated from many of the bodies being obtained from mines. This science, till lately, was without order or connection; but Werner has thrown much light upon this branch of natural history. According to him, minerals were divided into four classes, -earthy minerals, saline minerals, inflammables, and metals. Professor Mohs arranges minerals under three divisions or CLASSES. The characters of the first class, if solid, are sapid, with no bituminous odour; specific gravity, under 3.8. This class is divided into four orders, of which gas forms the first, and consists of two genera, hydrogen and atmospheric air. The second order is Water, the third, Acids, and the fourth, Salt. The genera of the fourth order are ten in number, of which common salt, saltpetre, muriate of ammonia, zinc, copper, and sulphate of iron are samples.

Bodies constituting the second class of minerals are insipid, their specific gravity being above 1'8. They consist of thirteen orders. The first is Haloide, or salt-like; the second is Baryte; the third, Kerate, or horny; the fourth, Malachite; the fifth, Mica, or Talc; the sixth, Spar. The seventh order is the Gem, consisting of thirteen genera, of which the diamond, the emerald, the topaz, the garnet, and the corundum are examples. The eighth order is Ore, of which tin, iron, zinc, and copper are examples; the ninth order, Metal, of which antimony, arsenic, and gold are specimens. The tenth order is Pyrites; the eleventh, Glance; and the twelfth, Blende. The thirteenth is Sulphur.

Bodies constituting the third class of minerals, if solid, are insipid; if fluid, they have a bituminous odour, their specific gravity being under 18. This third class consists of two orders; the first one being Resin, and the second Mineral Coal, which contains many species and varieties.

Of GEMS and PRECIOUS STONES, which are briefly explained in the body of the Dictionary, the following are the principal :

STONE is a general term, in Mineralogy, for natural, inorganic bodies, that are hard, brittle, and nearly insoluble in water. Of these the most valuable

METALS are an important branch of Mineralogy. In remote antiquity only

seven were known, viz., gold, silver, mercury, copper, iron, tin, and lead. But

modern discoveries have added considerably to the number, the most important of which are antimony, arsenic, cobalt, platinum, zinc, bismuth, manganese, iridium, tungsten, chromium, potassium, sodium, and lithium (the bases of the mineral and vegetable alkalies), and barium, strontium, magnesium, and calcium, the bases of the alkaline earths, &c. (See article METAL.) The number of bodies now classed as metals are forty-two. A few of the principal metals are here given in alphabetical order :

With Mineralogy, the important science of GEOLOGY, which teaches us the external structure of the globe we inhabit, is closely allied. "Geology," as Hugh Miller once observed, " is a glance in the direction of the eternity that has gone by," in the same manner as astronomy is a prolongation of our view through the infinite abyss of space, and as chemistry and botany extend our vision indefinitely through the material universe. Werner, who may be considered as one of the most intelligent writers on geology, supposes that the globe was once covered with a sort of chaotic compost, holding, either in solution or suspension, the component parts of the various rocks and strata which now present themselves at its exterior crust. The substances of which this crust is composed have been arranged by geologists under five classes. The first class comprehends the PRIMITIVE ROCKS, which were so named because it was assumed they were first formed through the agency of fire, and contain neither animal nor vegetable remains, nor even rounded pebbles: such are granite, serpentine, and porphyry. The strata lying immediately above the primitive rocks, where shells and fragments occasionally occur, are denominated TRANSITION ROocks, which consist of Graywacke and Transition limestone. The class above these is called FLOETZ, or Secondary Rocks, which abound in organic remains. The agencies of the wind, the ocean, and the weather produced those inequalities which exist on the earth's surface, and the water retreated into low lands and valleys, where depositions of sand, gravel, clay, &c., took place, and produced the Alluvial Rocks; the last class consisting of rocks produced by volcanic agency. It is presumed that these processes of Nature, operating through countless ages, are sufficient to account for the present condition and general appearance of the crust of the globe. It is manifest that all rocks, even the primitive ones, were once in a state of solution or liquidity, so as to admit of the innumerable forms and crystallizations in which they are now found.

As a corollary to the magnificent operations of physical science (says a modern writer) is the belief that life, which is spirit, would also be found coextensive with those great powers of Nature which we find moulding our own globe, with all its various phenomena of heat and light, its clouds and meteors, its seas and continents, and its endless varieties of organic existence. Spectral analysis has reinforced this mighty thesis, by positively showing that elements similar to those of our own world also enter into the composition of the orbs beyond us. The falling meteor which takes its fire by contact with the airenvelope of earth, impinging upon it from its own region of ether, is found to contain minerals common to this planet. Fact, analogy, the economics of Nature, her endless realms of marvel, and the deep instinct of the uplifted heart and eye-all combine to make it more and more likely that life is infinite in series. The more that our knowledge of the material world extends, and that we see the precise nature of the laws of life, the more do we perceive how essentially provincial were the old ideas of the relations which men bore to each other. Now that the study of physical science has generated the habit of dealing with facts as facts, and has filled the very air with a horror of anything like assumptions, we can hardly understand why past generations could have been satisfied with the narrow, dogmatic rules which we have inherited only to

set aside.

The rigorous demonstrations of MATHEMATICS admit of nothing that is vague; and therefore they have naturally led men to apply its principles to all those nobler sciences which admit of them; as Astronomy, Geography, Navigation, Physics, and Mechanics, which owe the great progress they have made to mathematical formule. Thus Geometry, so essential to the arts of design, by lending its forms and its language to the phenomena of crystallization, has elevated Mineralogy to the rank of an exact science.

In MECHANICAL SCIENCE the ingenuity of man is making wonderful advances. Engineering, Electricity, and Railways are effecting a vast social revolution throughout the entire globe, by which the great family of man may be eventually united in the peaceful bonds of friendship and commercial intercourse. Engineers, with their regiments of industrious workmen, have proved themselves, in numerous instances, the victors over the material forces of Nature; the makers of roads and railways, builders of bridges and viaducts, tunnellers of impassable mountains, delvers of mines, openers-up of strange lands, cutters of isthmus necks, diggers of canals, eager promoters of sanitary science, suppliers of water, drainers, builders, developers, iniprovers-whose vocation has turned so much of our once wholly wild and rugged earth into the agreeable and convenient world which we know and enjoy. The most important works which antiquity accomplished are not so remarkable as the works which are now performed through the agency of modern science, almost without notice. The Pyramids, the Appian Way, the Mausoleum, the Colossus of Rhodes, and the great Wall of China were certainly most wonderful undertakings; but the triumphs of engineering science, as recounted by the President of the Society of Engineers at one of their late meetings, are even more wonderful than the boasted "wonders of the world." There is the Pacific Railroad in America, now approaching to completion; the mountain railway which scales the Cenisian Alp; the Isthmus of Suez canal, now crowned as a practicable and successful enterprise, and justly called "one of the grandest works of modern time." The network of railway lines completed throughout India; the bridges thrown or throwing over the Mersey at Runcorn, over the Rhine at Kuilemberg, and over Niagara Falls in the last instance with a span of twelve hundred and sixty feet; together with such feats of modern engineering as the iron cradles which have been built in England for dockyard use at Bermuda, the Thames Embankment works, the London Main Drainage improvements, and the Millwall Docks-all these are really more wonderful in their way, and ten times more useful, than the prodigious efforts of ancient kings and conquerors.