RECENT ADVANCES IN SCIENCE 43 



as the tridymite-cristobalite transition temperature, while at 

 the same time it indicates that cristobalite has a stable 

 temperature range above that of tridymite (cf. Trans. Cer. 

 Soc. 17, 148, 191 7). 



The formation of cristobalite by the devitrification of 

 crown glass is noted by C. N. Fenner and J. B. Ferguson {Jour. 

 Amer. Cer. Soc. 1, 468, 1918), who ascribe the " milkiness " of 

 certain artificial glasses to the separation of crystals of this 

 mineral (cf. F. Gelstharp, ibid. p. 559). 



Several papers dealing with the crystals found in various 

 types of artificial glass have been published recently. N. L. 

 Bowen (Jour. Wash. Acad. Sci. 8, 88, 191 8) discusses the 

 analogies between the occurrence of heterogeneity in glass 

 and certain phenomena observed in igneous rocks. In a 

 second paper (ibid. 8, 265, 191 8) a hitherto unknown ortho- 

 rhombic silicate, BaSi 2 5 , is described as occurring in barium 

 crown glass and data are given for the melting-point and the 

 optical properties. A third paper (Jour. Amer. Cer. Soc. 1, 

 594, 191 8) is concerned with the investigation, by means of 

 petrographic methods, of the various types of stones (crystal- 

 line' particles) which are found in glass. The identification of 

 the crystals, together with the examinations of the structure 

 and texture, allows the origin of the stones to be determined. 



An interesting paper by G. V. Wilson (Jour. Glass Soc. Tech. 

 2» 177, 191 8) describes the formation of certain minerals in glass 

 furnaces. The crystallisation of the glass itself results in the 

 development of quartz, tridymite, wollastonite (/3-CaSi0 3 ), and 

 augite, while the action of the glass on fragments of lime- 

 stone gives, in addition to the metasilicates mentioned above, 

 melilite and tricalcium silicate (Ca 3 Si 2 7 ). The corrosion of 

 the materials of the furnace by the glass gives such minerals 

 as sillimanite, corundum, magnetite, oligoclase-felspar, and 

 biotite (apparently anhydrous). Various deductions are made 

 concerning the conditions under which the minerals formed. 



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

 University, London. 



Morphology. — An extensive study of shoots has appeared 

 from the pen of Prof. Warming (Mem. d. VAcad. Roy. d. Sci. 

 et Lett. d. Danemark), in which he distinguishes the follow- 



