as has been shown mathematically, that owing to the velocity of the hydrogen molecule, the earth cannot retain this gas in its atmosphere, then there must be a continued accession of hydrogen to the atmosphere from interplanetary space. If this is the case, it is probable that there must be a similar transfer of other gases, and therefore the authors of the paper sought in the spectra evidence of the presence of the characteristic lines of the spectra of nebuæ, of the corona, and of the aurora. Nebular lines were found in the tubes as above prepared; but in one, the gas of which had not been passed through the U-tube, and which contained traces of nitrogen and argon, a line was found very close to the principal green nebular ray, which did not appear in the other tubes, and which may indicate that the substance that is luminous in the nebulæ is really present in the earth's atmosphere. Several lines were found which may possibly be referred to coronal rays, but further study is necessary before this can be established. Still, more doubt attaches to the auroral rays, one of which seems to be identical with a strong ray of argon. The ingenious method devised for the collection of the gases, the demonstration of the presence of hydrogen in the atmosphere, and the possibilities opened up by this manner of attack render this research notable.
The progress which has been made in recent years in determining the useful and injurious dairy bacteria, and the means of controlling their growth, has greatly promoted the intelligent production and handling of milk for household consumption and in butter-making. In this work a number of the agricultural experiment stations have taken an important part. The Storrs Experiment Station in Connecticut is among this number, and its twelfth annual report, just issued, gives an interesting résumé of the something over two hundred types of bacteria which Professor Conn has found in dairy products during the ten years he has been engaged in this work. On the basis of his studies he proposes a classification of dairy bacteria. Although the total number of species found in dairy products is large, only a comparatively few occur with very great regularity. Professor Conn concludes that those of the region represented by his investigations consist chiefly of three groups of closely related bacteria. Of these the most abundant are Bacterium acidi lactici I. (Esten) and B. acidi lactici II. (new species), which constitute the first group. The former occurs almost universally in milk and cream, is nearly always present in sour milk, and has been found by far the most abundant in all samples of ripened cream examined. The second form, while very abundant in sour milk and cream, occurs in less numbers. Several of the pure commercial cultures for ripening cream in butter-making consist of bacteria of this type. The next most important group is represented by a species regarded as identical with B. lactis aerogenes, and includes a number of types of great similiarity, but with different physiological characters. It has been found almost universally in milk, but never in very great numbers. Some of the pure cultures used in Europe for cream ripening appear to belong to this group. Typical sour milk, with its tendency to fragmentation and its sour odor, Professor Conn thinks, is never developed without the aid of some of the organisms of this group. The third type is the Micrococcus lactis varians of the author. It is common in fresh milk, and is thought to exist in the milk ducts, which is not the case with the preceding types, the source of contamination with which is believed to be entirely external. It is commonly overgrown by the lactic organisms and is less common in old milk. While the classification of dairy bacteria is regarded as necessarily a tentative one, it is offered as a basis for bringing together the work of American dairy bacteriologists.
Another paper in this report bearing on the subject of dairying relates to
