September 3, 1915] 



SCIENCE 



311 



precipitated from these solutions after an 

 interval of time which varied with the dif- 

 ferent inoculations. These experiments show 

 the almost universal presence of organisms 

 capable of precipitating ferric hydroxide. In 

 order to show definitely that organisms were 

 responsible for this precipitation, sterilized 

 duplicates of the different cultures were pre- 

 pared and these did not show any precipita- 

 tion. 



It was found likewise that sohitions of dif- 

 ferent iron salts are affected in a different 

 manner during these inoculations. In some 

 solutions no precipitate forms, perhaps because 

 the salts used inhibit bacterial growth. In 

 other solutions, notably solutions of inorganic 

 salts, the precipitation of ferric hydroxide 

 takes place almost immediately, due to oxida- 

 tion by oxygen present in the solvent. Cer- 

 tain solutions were kept under anaerobic con- 

 ditions by passing carbon dioxide through 

 them and it was found that in some of them 

 ferric hydroxide was precipitated while in 

 others no precipitation took place. In general 

 the experiments have shown that precipitation 

 may take place from solutions of ferric, as 

 well as ferrous salts. 



Up to the present the writer's attempts to 

 isolate the lower bacteria present in soil and 

 water, which are responsible for the precipita- 

 tion of ferric hydroxide, have been unsuccess- 

 ful, but it is planned to prepare and to ex- 

 periment with various kinds of media in order 

 to bring about this result. Until this isola- 

 tion has been accomplished it will not be pos- 

 sible to study their morphology. 



The morphology of the higher iron bacteria, 

 unlike that of the lower, can be studied very 

 readily, as they can easily be distinguished 

 from other types due to their characteristic 

 form. While it is comparatively easy to culti- 

 vate such forms as Orenoihrix and Chlamydo- 

 ihrix in the laboratory, it is extremely difficult 

 to isolate them from other forms in order to 

 study their physiological processes. This is 

 because of the fact that numerous lower bac- 

 teria find lodgment on the threads of these 

 higher types, and are continually transferred 

 with them. 



One of the principal points of interest in 

 connection with these investigations has been 

 to note the relation that the iron bacteria 

 might have to the formation of iron ore de- 

 posits. It has been claimed that they play an 

 important part in the formation of numerous 

 small deposits of bog iron ore, and it seems 

 possible that their activities may in part be 

 responsible for extensive beds of sedimentary 

 iron ore as well. Further, the fact of finding 

 iron bacteria in underground mines opens the 

 possibility that certain underground deposits 

 of iron ore have been formed by them. 



The writer hopes soon to publish a detailed 

 report on the results of these various investi- 

 gations. 



E. C. Harder 



U. S. Geological Survey 



A TYPICAL CASE 



I HAVE read your correspondent's letter on 

 " A Typical Case Exemplified " in the number 

 of Science dated May 21, 1915, and I have 

 been struck by certain parallels and differences 

 in his case and my own case. I feel that per- 

 haps my case is worthy of citation. 



I, too, completed my work for the doctorate 

 in one of the oldest and largest of eastern in- 

 stitutions and, after having spent a year as 

 instructor there, came to the northwest at the 

 invitation of the president of the institution 

 and the head of my department with the 

 promise that I should have a fair opportunity 

 for original investigation. During my so- 

 journ of five years here, I have encountered 

 no such conditions as cited by your corres- 

 pondent and know of no such conditions in 

 any western institution with which I am fa- 

 miliar. Before completing my work for the 

 doctorate, I spent my time in three western 

 institutions as student and instructor. In all 

 of them, I found the research spirit freely en- 

 couraged. In my experience I have never 

 been told that research was personal and that 

 I must bear the expense and take time for it 

 from my recreation and sleep. As a rule, the 

 man imbued with the research spirit is not 

 likely to allow such obstacles to stand in his 

 way without surmounting them and is likely 



