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380 and the mountain-sickness for a time disappeared. Immediately on inhaling the oxygen there was a disagreeable dazzling, and at one time, after three inspirations, he became giddy and fell off his chair, but soon recovered. The author also describes the effects on himself of breathing a super-oxygenated mixture. With a mixture of 45 per cent., he could bear without injury a pressure of only 338 millimetres, which corresponds to the height of Chimborazo; and with 63 per cent. he was able to stand 250 millimetres (less than ten inches), and would have gone farther if his machine had been sufficiently strong. Since M. Bert's experiments, Messrs. Croce-Spinelli and Sivel have made a balloon-ascension to the extraordinary height of about 26,000 feet. They carried up with them a supply of oxygen, and, by using this after the manner indicated by M. Bert, they were enabled to live without inconvenience in an atmosphere of extreme rarity.

Lake Superior Gold-Mines.—Mr. Peter McKellar lately read, at the Toronto Institute, a paper on the gold-mines of Lake Superior. Some Indians from the vicinity of Thunder Bay, in 1871, brought to Mr. McKellar, at Fort William, several specimens of quartz, from an examination of which he was led to think that valuable gold-mines existed in the locality. The paper then described the lodes that had been discovered. The first was the Jackfish Lake lode, which lies about eighty miles west of Thunder Bay. From this lode 126 pounds of ore were sent to the Wyandott Smelting-Works, and yielded at the rate of $500 per ton; of this sum, $40 was derived from silver, and the remainder from gold. The Partridge Lake lode, lying about 100 miles northwest of Thunder Bay, yielded about $30 per ton of ore. In the summer of 1872 another lode, called the Heron Bay lode, was discovered, about 150 miles northeast of Fort William. It was similar to the Jackfish Lake lode, excepting that its yield of gold and silver was not so great. Mr. McKellar holds that these mines might be worked very economically, and that they would yield as large profit as, if not larger than, any others in the world. In the lodes already discovered, the gold was found very evenly distributed through the ore, which is said to exist in large quantities. Iron, lead, and other metals, occur in the neighborhood. The difficulties in developing these mines have been very great, owing principally to the unsettled state of the country. The Indians have refused to help in working the mines until some settlement shall be come to with them, as they fear that white men may come and dispossess them.

Researches on the Zodiacal Light.—Prof. Arthur W. Wright, of Yale College, who for upward of a year has been closely investigating the zodiacal light, has, by means of an apparatus of his own contriving, succeeded in demonstrating that this light is polarized. In the American Journal of Science, for May, Prof. Wright describes his polariscope, and the results at which he has arrived in the course of his researches. He finds that the plane of polarization of the zodiacal light passes through the sun. In no instance, when the sky was clear enough to render the bands visible, did their position, as determined by the observations, fail to agree with what would be required by polarization in a plane through the sun; not the slightest trace of bands was ever seen when the instrument was directed to other portions of the sky.

Having thus determined the fact of polarization, the next step was to ascertain what percentage of the light is polarized. For this purpose, the author again had to devise novel apparatus. The amount of polarization was determined to be, "with a high degree of probability, as much as 15 per cent., but can hardly be as much as 20 per cent."

The fact of polarization implies that the light is reflected, either wholly or in part, and is thus derived originally from the sun. The spectrum of the zodiacal light is not perceptibly different from that of sunlight, except in intensity. The author adds: "A particular object in these observations was to determine whether any bright lines or bands were present in the spectrum, or whether there is any connection between the zodiacal light and the polar aurora." The results give a decidedly negative answer to this question. "This is important