392 SCIENCE PROGRESS 



cultures is much to be deplored. It further assumes that the 

 oxidation of ferrous compounds is the work of an enzyme 

 secreted by the organism. As shown above, the facts now at 

 our disposal render this standpoint indefensible. Lately also 

 Harder, of the U.S. Geological Survey, has promised us the 

 proof that a large number of the lower bacteria are capable of 

 oxidising ferrous compounds. There is every probability that 

 quite a large number of micro-organisms are capable of doing 

 this, for, if we assume the correctness of Campbell Brown's 

 theory, all bacteria capable of abstracting soluble organic 

 matter incidentally combined with iron will by the absorption 

 of this organic matter remove that to which is due the retention 

 of so much iron in the soluble form. It is probable that 

 interesting results will be obtained along these lines. 



Are the Iron-Bacteria to be regarded as Rock Builders ? 



This question has been dealt with from time to time, but 

 it is only recently that the issue has been placed on a satis- 

 factory basis. Within recent years Molisch has examined 

 sixty-one samples of ferruginous stones from various parts of 

 the world, and in fifty-seven he found no traces of Iron-bacteria. 

 In the remaining four Iron-bacteria were undoubtedly present, 

 but it is difficult to remove the impression that these bacteria 

 were not obtained from a modern sediment on the surface. It 

 is to be hoped that we shall later receive a more detailed treat- 

 ment of the four stones in question. If the bacteria were 

 found in the body of the stone we should be in possession of a 

 fact of great interest. The writer has recently examined forty- 

 eight of the ferruginous rocks of Great Britain and found four 

 to contain the remains of iron micro-organisms. These four 

 stones were all obtained from the Frodingham ironstone of 

 Lincolnshire, and contained the remains, not of bacteria, but 

 of an iron-mould to which the name Phycomycites Frodinghamii 

 was given. This organism was present in the organic remains 

 that are plentifully found in this rock ; and while during its 

 lifetime it probably had the physiological characteristics of 

 the Iron-bacteria of the present day and thus enriched the 

 ferruginous content of the stone containing it, it cannot in any 

 sense be regarded as a rock builder. 



