THE PROGRESS OF SCIENCE. 



559 



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 evi- 

 dence of the presence of the characteris- 

 tic lines of the spectra of nebua?, 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 ni- 

 trogen 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 sub- 

 stance that is luminous in the nebulae is 

 really present in the earth's atmosphere. 

 Several lines were found which may pos- 

 sibly 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 produc- 

 tion and handling of milk for household 

 consumption and in butter-making. In 

 this work a number of the agricultural 

 experiment stations have taken an im- 

 portant part. The Storrs Experiment 

 Station in Connecticut is among this 

 number, and its twelfth annual report, 

 just issued, gives an interesting resume 1 

 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 bac- 

 teria. Although the total number of 

 species found in dairy products is large, 

 only a comparatively few occur witli 

 very great regularity. Professor Conn 

 concludes that those of the region repre- 

 sented 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 bac- 

 teria of this type. The next most im- 

 portant group is represented by a spe- 

 cies regarded as identical with B. lactis 

 aerogenes, and includes a number of 

 types of great similiarity, but with dif- 

 ferent 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 tend- 

 ency to fragmentation and its sour odor, 

 Professor Conn thinks, is never devel- 

 oped without the aid of some of the or- 

 ganisms 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 exter- 

 nal. 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 bear- 

 ing on the subject of dairying relates to 



