to fathom the mystery of gravitation,-that our inquiries should be limited to an investigation of the laws of nature, without seeking to unfold the hidden cause of life and motion. But if an examination of the laws and phenomena of motion should lead to a fortunate discovery of their cause, are we to close our eyes? We admit that the cause of gravitation is quite as mysterious as that of life; but we maintain that all mysteries are simple, when once we obtain a key to their solution. We discover that a familiar and well known agent, which is every where present, is the cause of molecular attraction, and lo! the mystery of gravitation vanishes. We perceive that the same universal agent attracts and arranges the atoms of salts, metals, etc., into definite forms, as in chrystallization, which may be termed the lowest grade of organization. When united with other elements in certain proportions, it endows them with more active powers of attraction, by which they appropriate the molecules of other matter to their own structure and growth, when life begins to dawn, as in all the most simple forms of organization which spring from putrefaction. Thus we learn, that it is almost impossible to draw the boundary line between chemical and vital affinities. The one insensibly passes into the other— and neither can go on without caloric. Under the influence of a high summer temperature, while chemical action is going on rapidly, innumerable forms of life are produced. A portion of the decomposing elements combines chemically to form water, carbonic acid, etc., while another portion is combined by a higher grade of affinity, into definite forms of living matter, capable of attracting fluid nourishment from the surrounding me dium, converting it to their own nature,-and of resisting chemical action. It has been proved by the experiments of Prevost and Dumas, that fluid albumen is converted into a white coagulum by electricity, composed of globules in series and aggregates, as in the primitive tissues of living animals. Dr. Edwards has further established by experiment, that the same result is produced on albumen, gelatine, febrin, and mucus, by heat, and by alcohol, acids, and other agents which impart heat. The above experiments are of great importance to the Physiologist, and show clearly the agency of heat, or electricity, in producing the low. est gradation of vital attraction and organization,-that they have the power of uniting the chemical molecules of watery and semi-transparent fluids into compound molecules, which become visible globules with the microscope, and of arranging them into organic series. By a continued supply of this subtile fluid, they are endowed with the still higher power of attracting the molecules of dead matter; of re-combining and changing them into living molecules; and of appropriating them to their growth by the beautiful mechanism of vital affinities. Can it be supposed for a moment that there are two or more specifically distinct powers of attraction?—one of cohesion and chrystallization,-another of chemical attraction,—and another of vital affinity? The idea is altogether at variance with the simplicity of Nature, who never employs more agents than are requisite to perform her operations. Can it be seriously maintained by any philosopher that the cohesion of a muscle is the result of a power radically different from that which holds together the atoms of wood, stone, metals, etc.? or that the capillary circulation of plants and animals is owing to a power of nature distinct from that which causes ordinary capillary attraction? The difference is only in degree, as will appear from a further examination of vital properties. It was supposed by Hoffman that the vital principle was a subtile ether, diffused throughout nature. Sauvages embraced the same general doc. trine, maintaining that electricity was the living principle. Mr. Abernethy also taught, that irritability, the fundamental property of all life, was the effect of a subtile, mobile, invisible matter, superadded to the structure of muscles, and other forms of animal and vegetable matter, as magnetism is to iron, and as electricity is to the various substances with which it may be united.* Some of the most distinguished philosophers of modern times have considered electricity as the great vivifying principle of nature. Dr. Priestly observes, that electricity seems to be an inlet into the internal structure of bodies, on which all their sensible properties depend,'-and he adds, in the spirit of prophetic sagacity, by pursuing, therefore, this new light, the bounds of natural science may possibly be extended beyond what we can now conceive. New worlds may be opened to our view, by a new set of philosophers, in quite a new field of speculation.' Sir Humphrey Davy, believed that the slow and silent operations of electricity on the surface of the earth, would be found immediately and importantly connected with the order and economy of nature. The celebrated John Wesley, long before maintained, that electricity was the animating principle of nature. Mr. Maden observes, that 'a day, in all probability, will come, when the progress of science will trace the analogies of the subtile spark which pervades all space, with that material fire which fills the nerves with life and heat, and communicates vigor to every fibre of the heart and its remotest vessels. The nature of the nervous power may then be better understood, and that invisible aura which fans the blood and invigorates the body, be known to us by something more than its effects.'† It has been profoundly observed, by a distinguished writer of the present day, 'that all scientific knowledge leads up to principles, characterized, not less by their simplicity, than by their comprehensiveness, that the greatest operations, and the noblest forms of nature, are distinguished by simplicity. It will be obvious to the intelligent reader, that if we have demonstrated that the latent caloric of all bodies is the basis of elecricity, we are supported by the highest authorities, ancient and modern, in the doctrine that caloric is the living principle of the world. That solar heat is intimately connected with the vital principle, is obvious from its effect in multiplying endless forms of animal and vegetable existence. It is estimated by naturalists, that the whole earth contains one million five hundred thousand species of plants and animals, by far the greatest number of which inhabit the regions of perpetual summer. The tropical ocean teems with unnumbered forms of life, from the simplest gradation of gelatinous animalcules, up to the most complicated Inquiry into Hunter's Theory of Life, p. 39. + Infirmities of Genius. + Fox. organization of the finny tribes. Lamarck supposed that it contained four hundred thousand species of zoophytes, many of which absorb the lime that is carried down by rivers and springs into the sea, and convert it into mountains and islands of organic rocks. Madrapores and sponges, seafans and fuci, cover its hills, and shelter in its valleys. Countless tribes of beautiful shells, of rainbow hues, float through its coraline groves, and die on its sunless floor. The land is covered with -Queen lilies, the painted populace, Who dwell in fields, and lead ambrosial lives;' Every mouldering leaf and spear of grass, is the nidus and pabulum of myriad forms of animalcule existence. The air is filled with the music and incense of breathing life. All nature is in a state of transition from life to death, and from death to life. What can be more impressive than the vast but silent power of the sun on the approach of Spring in our own latitudes? He looks down with regal splendor upon the earth, when all nature seems regenerated, and bursts forth into a new existence, under the enlivening influence of his genial rays. Every plant, tree, and flower, obeys his call. The fields and forests put on their beautiful robes. Sweet scented herbs spring up on every side, filling the air with delicious odours. The buds of trees expand into leaves, branches, and flowers, which, being supplied with nutritive juices, are changed into fruits. The solitudes break forth into singing, and all nature resounds with gladness and melody. But in the dreary regions of perpetual cold, no sounds of life are heard. An awful stillness reigns, and nature seems to have lost the powers of production. We may be told that heat cannot be the vital principle, because when greatly augmented, it destroys life. It might as well be maintained that atmospheric oxygen is not necessary to life, because, if the lungs be sup plied with pure oxygen gas, inflammation and death very soon follow. When the vital principle is supplied in due proportion throughout the system, healthy action is the result,-when in excess, or deficient, disease or death ensue. Actions which are pleasurable and healthy, when in moderation, become painful and morbid when excessive, as in inflammation. It has been long known, that during warm, sultry weather, nearly all stagnant pools of water, containing dead animal and vegetable matter, in a state of decomposition, are filled with thousands and millions of animalcules, insects, etc., and that they become covered over with a green vegetable substance-termed by botanists the conferva fontanalis,-that if a paste be made of flour and water, and placed in a warm situation, it soon becomes covered with a miniature forest of teeming vegetation,that the same effect may be produced after boiling the water for hours, and putting it into tightly corked bottles, if kept in a warm temperature; from which it was inferred, that they were produced by spontaneous generation. Many other striking facts have been discovered, which seem to show conclusively that caloric is the proximate cause of spontaneous vitality. The experiment was made some years ago in England of bringing up aluminous earth from a depth of three hundred feet below the surface of the Thames valley, inclosed in a glass vessel so as to prevent the access of any small seeds which might be floating in the atmosphere. After a few days exposure to the warm sun, it became covered with luxuriant vegetation. Worms have been repeatedly found in the bowels of new born infants-in the liver and veins of men, and other animals-also, between the external coat of the bowels, and the peritoneal lining of the abdomen of trout. He who wishes to behold the simplest gradations of life, as they emerge from a state of inanimate existence, has only to enter some deep mine, where, unmolested by winds and changing temperature, moulds and mosses cover the damp walls. Their fragile and gosamer filaments seem to be composed chiefly of water. A breath will destroy them. Now it is an interesting query whether these simple and evanescent forms of life have any other origin than spontaneous production. If they have, the evidence is beyond our scrutiny. How stupendous that wisdom which has so ordained the laws of nature, that teeming life springs from death; Throughout the air, the ocean, and the earth, See matter quick, and bursting into birth.' Spontaneous generation is only a modification of ordinary generation, and is regulated by laws as definite and uniform as the production of genera and species from pre-existing types. But we have been informed by some learned divines, that this doctrine is impious, and contrary to the Bible. To such interpreters of the sacred volume, we would only answer, that the known laws and phenomena of nature can never be in opposition to the immutable cannons of eternal truth. Is it irreverent, or unphilosophical, to maintain that the Deity has impressed upon matter the properties and powers of vitality? As well might we deny that he has endowed matter with the powers of attraction and repulsion. Pursuing this investigation, it would be highly interesting to know whether, if all the animals and plants which now inhabit the earth were destroyed, a similar variety of families, tribes, and orders, would again gradually emerge into life, during the progress of long goological cycles, under the operation of the existing laws of nature? Has the Creator of all things commissioned the elements of nature to execute his laws in the production of beasts, birds, and fishes from inorganic matter? And have they advanced gradually from one stage of existence to another? It was supposed by Lamarck, that species are each of them endowed with indefinite powers of improvement in organization, under favorable circumstanThe successive production and extinction of various animal and vegetable tribes, during successive geological epochs, offer some useful hints in the prosecution of this novel investigation. In the first book of his Metamorphoses,-a poem which displays a profound knowledge of the Pythagorean philosophy,-Ovid maintains that all animals after Deucalion's flood, were gradually produced by the action of solar heat on the teeming earth. This was the common belief of all antiquity. ces. We have shown that every thing is full of latent caloric-that when it is combined with the atoms of other matter in one proportion, it is the cause of solidity-that when it is increased in quantity, it is the cause of solution, capillary attraction, and chemical affinity,-that when it is supplied in other modes, and proportions, it causes irritability, and the higher properties of life. Thus we perceive, that the active principle of nature, when united with ponderable matter, in different modes and proportions, produces all the beautiful gradations of power, from the simplest forms of attraction, up to the most complicated organization and vital affinities. If these positions be well founded, it follows that the vital principle must be a constituent portion of all matter, from the surface to the centre of the earth-that in reality, there is a latent principle of life existing in all things, 'In flower and tree, and every pebbly stone ready to burst forth into activity,-multiplying endless creations of organized beauty. It is well known that all the reptile and insect tribes are reduced to the torpor of death, during winter, in the higher latitudes, and that they are awakened to life by the genial influence of returning spring. The most rigid scrutiny of man can trace no irritability in frozen fish. Captain Franklin states, that in the polar regions, fish were often frozen throughout, like a mass of brittle ice, which were soon re-animated when placed in water at the temperature of 40° or 50° Fahrenheit. The same thing is said to have occurred repeatedly in Rhode-Island, and other parts of New-England, during excessively cold weather. Dr. Johnston, of this city, informed the writer that he saw a small sun-fish taken out of a pond in Dutchess county, which was kept in a frozen state for six weeks, and afterwards revived, when placed in common well water. He relates a similar fact in relation to a newt. When treating of molecular attractions, we stated that all trees and plants are mere aggregations of capillary tubes, through which many hundred million tons of fluid matter is forced up by the power of capillary attraction, under the influence of solar heat, but was uniformly arrested by cold, that without caloric there could be no fluidity,-no capillary attraction,-no circulation of sap, and no vitality. That heat is the agent by which fluids are forced through the capil lary tubes of trees and plants, is proved by the following facts: Two similar vine plants were placed in two vessels of water. The stem of one was left in the open air, and the other introduced through the glass into a hot house, when the buds of the latter soon expanded, and the water was rapidly exhausted; while the buds of the other swelled slowly, and the water was slowly diminished.† During the day, when the heat is greatest, the rise of sap is most rapid, and diminishes, or ceases, during night. Cloudy weather also diminishes the ascent; and a gleam of sunshine increases it. Mirbel found by experiment, that the force of capillary circulation, in a healthy grape vine, was equal to the pressure of thirty inches of mercury, and Du Hamel, that during spring, on a frosty day, when the sun shone on a cut vine, the |