RECENT AIDVANCES IN SCIENCE ^t 



exists, and that the only definite compound is the monohydrate, 

 FeaOj . HaO. All the others are amorphous colloidal mixtures, 

 but the monohydrate exists in two crystalline forms, goethite 

 and lepidocrocite, both of which occur in nature. No crystal- 

 line hydrate, however, has been prepared synthetically. The 

 fibrous mineral, turgite, whose composition is approximately 

 2Fe203.H20, is regarded as a solid solution of goethite and 

 haematite, with possibly some absorbed water. L. J. Spencer 

 {Min. Mag., 18, 339, 1919), on the other hand, concludes, on 

 the basis of its optical properties and dehydration phenomena, 

 that turgite should be regarded as a definite mineral species. 



The conclusions of R. B. Sosman and J. C. Hostetter {Journ. 

 Amer. Chem. Soc.,28, 807, 1188, 1916), regarding the existence 

 of a series of solid solutions of haematite and magnetite, are 

 called in question by T. M, Broderick (E'cow. Geo/., 14, 353, 1919). 

 The latter admits the possibility of solid solutions, but holds 

 that many of the natural intermediate forms show a lack of 

 homogeneity when examined microscopically by metallographic 

 methods. 



An interesting note by J. B. Ferguson {Journ. Wash. Acad. 

 Set., 9, 539, 1 919) reveals the fact that ferrous oxide in lavas 

 is not oxidised to any great extent by steam at high tempera- 

 tures, and hence a high content of ferric oxide in a magma is 

 not incompatible with the presence of much steam. A theo- 

 retical paper on the relations between the lower oxides of iron 

 and oxygen, by A. Smits and J, M. Bijvoet {Proc. Akad. Am- 

 sterdam, 21, 386, 1 91 9), may also be mentioned. 



The ortho- and meta-silicates of the alkaline earth and 

 related metals have been prepared by F. M. Jaeger and H. S. 

 van Klooster {Sprechsaal, 62, 256, 1919), and some of the 

 optical properties determined. A linear relation between the 

 melting-points of the metasilicates and the atomic weights of 

 the metals is found to hold in certain groups. In a further 

 paper, C. N. Fenner {Journ. Soc. Glass Tech., 3, 116, 1919) 

 reiterates his conclusions on the stability of the silica minerals, 

 while a revised theoretical explanation of the same system is 

 given by A. Smits and K. Endell {Zeit. anorg. Chem., 106, 143, 

 1919). 



BOTANY. By E. J. Salisbury, D.Sc, F.L.S., University College, London. 



The group of the Actinomyces has been the subject of several 

 important papers, notably those of Drechsler (5o/. Gaz. 191 8), 

 Waksman {Journ. Bacteriology, 191 9, and Soil Science, 19^9), 

 and Waksman and Curtis {Soil Science, 191 8). For a long 

 time placed with the Bacteria, the group differs in the posses- 

 sion of true branching, which is profuse, in the fungal t3^pe of 



