The violence and the magnitude of some of these reactions almost baffle the imagination. Let the reader drop a piece of calcium carbide as large as a small marble into a little water in a cup; there is a rapid action, a gas (acetylene) is given off, which burns with a smoky flame if a lighted match is held over the cup. (The experiment should be tried in the open air.) So much heat is generated in the reaction that the cup becomes hot. Nearly four per cent. of the earth’s outer crust is calcium; all this was at this period of the earth’s history in the form of carbide. Imagine all the vast limestone mountain ranges of the present day as carbide, and try to realize the effect when water fell on any considerable area. The heat generated would be so enormous that in a moment the acetylene would ignite and burn, forming oxides of carbon and water vapor, which would in turn decompose, throwing the jets of glowing hydrogen and oxygen vast distances into the atmosphere, there to cool and reunite to water. The decomposition of other carbides, of the hydrides and silicides, as well as the formation of hydroxides by the action of the lighter metals on water, would produce similar phenomena, as the substances formed are combustible gases, or liquids or solids easily volatilized. This is no wild fantasy, but a conservative statement. Similar reactions are taking place at the present day in those stars whose cooling process has advanced far enough; a case in point is that of the so-called ‘temporary stars.’
Extremely violent reactions are taking place constantly in the atmosphere of the sun. The sun’s chromosphere, or outer layer of its atmosphere, consists mainly of hydrogen, and jets of glowing hydrogen are thrown to great heights above the chromosphere; these jets or ‘prominences’ have been frequently observed to have a height of 100,000 miles, and prominences of more than double this height are reported by observers. The most conservative estimates assume temperatures of the sun’s surface so enormous that that of the electric furnace is insignificant in comparison, and we can have no conception of the chemical changes occurring under such conditions. Whether one believes, with Lockyer, that the chemical ‘elements’ are disassociated by the sun’s heat into simpler substances or not, it is clear that very violent chemical reactions are in progress, and if we realize that the known chemical reactions increase in intensity with increase in temperature, it does not seem strange that at the sun’s temperature the reactions occurring should cause disturbances like those observed.
Returning to the earth, let us consider the products of these violent reactions. The hydrogen and hydrides of boron, silicon, sulphur and carbon, combined with the oxygen of the atmosphere, forming water and boric, silicic, sulphurous and carbonic acids, which in turn acted on the metallic oxides and hydroxides, forming sulphites, carbonates, borates and simple and complex silicates; some quickly, some slowly, some at low temperatures and atmospheric pressure, others at high temperatures in liquid or semi-liquid condition and under the pressure of rock masses above. To determine the relative age of existing rock layers, or the mode of their formation, whether by eruptive action, by surface heat, by deposition of finely divided material under water, or by metamorphic changes of the cooled silicate under subsequent action of water, pressure and heat, is the province of the geologist. The present writer refrains from an opinion whether any of the first formed solid crust could or could not survive to the present day in its primary form, considering the exposure to water, acids, heat and pressure which it suffered.
Yet an idea may be formed of the condition of the earth’s surface when it had cooled so far that the more violent chemical action had ceased. It consisted chiefly of silicates, simple and complex; of some of the original binary compounds, which are scarce affected by water or acids, such as the silicide of carbon (carborundum), of stable oxides, chlorides and sulphides, with other compounds in smaller proportion, and free elements in greater proportion than at the present day. Everywhere, from crevices in the surface, hydrocarbons, phosphoretted hydrogen (phosphine) and ammonia were issuing as gases; the atmosphere was heavy with these gases and with carbon dioxide.
No scientific observations thus far show how or from what definite compounds plant life or animal life was first evolved from lifeless matter; but it is certain that the materials were much more abundant and the conditions more favorable at the period when it was evolved than at the present day. An ocean much warmer and less saline than now, a damp atmosphere like that of a hothouse, an abundance of plant food and a choice of raw material, were at hand. The chief foods required for plant life are nitrogen in the form of ammonia or nitrates, carbon dioxide, phosphorus as phosphates, sulphates of lime, of magnesia and of the alkalies, and water. As to the raw material for the first formation of the living cell, it is impossible to say what compounds of carbon were employed; suffice it to note that the known simple and complex binary compounds of carbon were there ready for use; the hydrocarbons, carbon monoxide and carbon dioxide were oozing from the earth’s surface, from the ocean floor as well as from the land, or hanging heavy in the air above it. If warmth or increased pressure were desiderata, an ocean warm to its greatest depths could afford any pressure required. From the decomposition of the nitrides and phosphides below the surface, ammonia and phosphine were escaping into the ocean and into the air. The conditions then during long periods of time were especially favorable for marine life, and as sand and mud accumulated on the rocky surface of the earth, for land plants; the absence of a thick soil being more than compensated for by the abundance of plant food, notably of carbon dioxide and ammonia.
The statement may be found in excellent modern text-books of chemistry that ammonia is always formed by the decomposition of plants and animals, accompanied by the further statement that ammonia is a requisite for plant food. No plants—no ammonia; no ammonia—no plants. If this were true, the beginning of plant life would indeed have been a struggle for existence; that it is not true is shown above. This decomposition of nitrides has ceased practically on the actual surface of the earth at the present day because the nitrides have all been decomposed; yet it may be mentioned that specimens of rock freshly quarried in Sweden were recently found to give off ammonia when wet with water, showing the presence of nitrides. Below the actual earth’s surface it is probable that nitrides still exist in large quantity, for ammonia is one of the constituents of volcanic gases; to believe that volcanic ammonia is a product of plant or animal decomposition is difficult; to suppose it formed by the action of steam on nitrides in the earth’s interior is simple.
Much the same may be said of the presence of carbides. While they no longer exist on the surface, there is no doubt of their existence in the interior of the earth, and the volcanic gases contain their decomposition products. In this connection the theory—first put forward by Mendelèeff and since supported by Moissan—of the origin of petroleum, may be mentioned. These writers favor the hypothesis that it was formed by the decomposition of carbides by water under pressure; and while the evidence at hand perhaps favors the belief that the petroleum of the more important oil fields owes its origin to decomposition of the lower forms of marine animal life, yet there can be no doubt that petroleum may be formed by carbide decomposition, and it seems probable that natural gas is in part at least a result of the same action.