indifferently, but he used Latin and symbols taken from alchemical manuscripts to designate chemical substances.
THE CONDITIONS OF CHEMICAL ACTION.
It has long been known that the presence of water is necessary in order that many chemical reactions shall take place, and that substances which ordinarily unite with great violence have no action upon each other when thoroughly dried. It has even been found possible to distil phosphorus in an atmosphere of oxygen, provided that the phosphorus and oxygen are both perfectly free from any trace of the vapor of water. It has, however, been found by a number of experimenters that hydrogen and oxygen will unite with each other when heated, even if dried. This exception seemed to be due to the fact that when the two gases unite, water is formed, but theoretically the first particles of the gases could not unite unless a trace of water were present. This led Professor Brereton Baker, of Dulwich College, who has done much work along this line, to the idea that the gases used might not be perfectly pure. The oxygen and hydrogen for the experiment are generally formed by the electrolytic decomposition of dilute sulfuric acid or caustic potash. But several years ago Professor Morley, of Cleveland, pointed out that the gases from these sources contain traces of impurities. By electrolyzing highly purified barium hydroxid, Professor Baker was enabled to avoid previous errors and obtain absolutely pure gases. The mixed hydrogen and oxygen were thoroughly dried (over phosphorus pentoxid) and sealed in glass tubes. After ten days' drying the tubes were heated to 600 degrees Centigrade and remained perfectly unchanged, while companion tubes, similarly prepared, except as to the drying, exploded in every instance. In tubes which had been dried only two days, the hydrogen and oxygen united slowly to form water, but did not explode. In order to test the effect of higher temperatures, tubes were prepared with a silver spiral attached to platinum wires which were sealed into the glass. The spiral was heated until the silver melted, but no explosion took place and no hydrogen was formed. When, however, a platinum spiral was substituted the tubes did explode, probably owing to the catalytic action of the platinum. From the experiment with the silver wires it is evident that when perfectly dry, hydrogen and oxygen do not combine with each other, even at 1,000 degrees Centigrade, the melting point of silver.
The experiment with the partially dried gases seems to lend confirmation to the theory of Dr. Armstrong that without an electrolyte no chemical action is possible; for though water is but slowly formed, it is present in far greater quantity than is necessary to bring about the action, yet no explosion follows. It may be assumed here that the water formed by the union of very pure gases is itself very pure, and since pure water is not an electrolyte, this water should not cause an explosion of the gases.
THE PERIODICITY OF SOLAR PHENOMENA.
In the Astronomische Nachrichten (Numbers 3,723-24) F. Hahn has propounded a new theory to explain the periodicity of solar phenomena. The various theories, which have been advanced hitherto in explanation of the periodic phenomena which occur at the sun, have failed to take into account the so-called solar atmosphere, the light and heat absorbing envelope which surrounds the photosphere. The importance of this atmosphere, in connection with its influence on the radiant energy of the sun, has never been properly appreciated, although attention was called to it by Langley, who showed that the sun, if deprived