December i, 1923] 



NA TURE 



807 



referred to in Nature (vol. 112, p. 460), have now been 

 ! printed in the Proceedings of the Academy, vol. 9, 

 pp. 292 and 296. The first deals with the marginal 

 belts of coral seas, and it is pointed out that platforms 

 of low-level abrasion are not known in association with 

 the islands in the cooler zones of the Pacific region, 

 while their depth below sea-level is not so uniform 

 where they do occur as to satisfy Daly's theory of 

 glacial control. If we accept glacial control, as 

 Davis is quite willing to do, the evidence for sub- 

 sidences of various degrees of magnitude, as put 

 fonvard by Darwin, remains unimpaired. The 

 second paper deals with the argument based on the 

 uniformity of depth of the lagoons within adjacent 

 atolls, and the author urges that level floors arise 

 through infilling with detritus, which is spread out 

 evenly by the wash of marine water. 



Pl.ants of the Middle Old Red Sandstone. — 

 R. Kidston and W. H. Lang (Trans. R. Soc. Edin., 

 vol. 53, pt. 2, p. 409, 1923) have investigated and 

 completely described the remains of Palceopitys 

 Milleri McNab, a plant originally found by Hugh 

 Miller in beds containing Coccosteus decipiens near 

 Cromarty. The authors confirm McNab's observation 

 of bordered pits in the tracheides ; but they are 

 unable to decide, in the absence of any evidence as 

 to the fructification, whether the genus should be 

 referred to the gymnosperms or to the pteridophyta. 

 In either case it is probably a distinctly archaic type. 

 The same authors {ibid. p. 405)' describe, and figure in 

 a photographic plate, an extremely beautiful speci- 

 men of a plant with numerous stems spreading radi- 

 ally from a basal region. This was collected by 

 G. Edward, and described by him in 1888. Edward 

 placed it, with his other specimens from Scotland, 

 in the Manchester Museum. Its locality is the Hill 

 of Forss, Waas, Caithness, and it is of Middle Old Red 

 Sandstone age. Sporangia set on short stalks occur ; 

 but G. Hickling, when on the staff of the University of 

 Manchester, examined these for spores in vain. The 

 authors now give a name to the plant, Hicklingia 

 Edwardi, and seek its affinities in forms from the 

 famous Rhynie cherts. It may be found, indeed, that 

 Hicklingia extends our knowledge of the Rhyniaceae. 



Daily and Seasonal Variations of Fog. — The 

 Meteorological Office of the Air Ministry has recently 

 issued a Professional Note, vol. iii.. No. 33, by Mr. F. 

 Entwistle, on the above subject. Observations of 

 fog from April 1920 to March 1922, a period of 2 

 years, were grouped for each month at Croydon, 

 Lympne, Cranwell, and Dungeness for all hours of 

 the day for which observations were made. A 

 temporary increase in fog is shown in the early 

 morning, a maximum being reached between one and 

 two hours after sunrise. The summer maximum 

 occurs about three hours earlier than the winter 

 maximum. Lxjndon smoke naturally somewhat affects 

 the general visibility at Croydon, being influenced by 

 the direction of the wind. Increase of fog in the 

 early morning is said to be due probably to eddy 

 motion mixing the layers of air near the surface. 

 There is generally less fog during the afternoon, 

 between midday and 6 p.m., than at any other time 

 during daylight. For civil aviation it is considered 

 desirable to arrange early morning services, before 

 the maximum fog intensity is reached, while for 

 ordinary services the middle of the day is the best 

 time. In the winter sea.son the larger proportion of 

 slight fogs at Croydon are doubtless due to town 

 influence. The thick fogs at Lympne are due chiefly 

 to low cloud caused mainly by winds between south 

 to south-west, so that the high ground of the North 

 and South Downs is enveloped. The small amount 



NO. 2822, VOL. I 12] 



of fog in winter at Dungeness seems to suggest that 

 the best position for an aerodrome in winter is on 

 the coast near sea level. In the summer months 

 thick fog is frequent at Lympne and Dungeness ; at 

 Dungeness it is chiefly sea fog caused by the relatively 

 warm air from off the land passing over the cooler sea. 



Formation of Ozone in Flames. — Prof. Manchot, 

 of ?^Iunich, communicated to the autumn congress 

 of German Chemists at Jena a paper on the formation 

 of ozone in flames. Parts of the flame which have a 

 temperature of 750° C. only contain ozone, as can 

 be proved by the silver reaction. The formation 

 of ozone does not depend on the nature of the com- 

 bustible gas, ozone being formed with hydrogen, 

 carbon monoxide, methane, acetylene, cyanogen, etc. 

 A flame of oxygen and hydrogen gas of 1300°- 1900° C. 

 contains about o-i per cent, of ozone, one of acetylene 

 and oxygen of 2100° C. about i per cent. The 

 latter blackens silver as if it were covered with soot. 

 The thermal formation of ozone, and also the forma- 

 tion from hydrogen peroxide, are not possible, since 

 ozone is also formed within a flame of perfectly dry 

 carbon monoxide. It is probable that the ozone is 

 formed by the action of electrons. 



Standardising Piezo-Electric Apparatus. — The 

 extensive use of the piezo-electric properties of 

 crystals in the measurement of transient pressures 

 such as those due to an explosion makes it necessary 

 to inquire into the validity of the method used to 

 standardise the apparatus! It has generally been 

 considered sufficient to apply a steady known pressure 

 to the crystal and to note the effect. In a short paper 

 in the November issue of the Philosophical Magazine, 

 Dr. D. A. Keys, of the McGill University, Montreal, 

 points out that as the standardisation experirnent is 

 an isothermal and the ordinary use an adiabatic one, 

 there may be a difference in the piezo-electric constant 

 of the crystal in the two cases. He examines this 

 possibilitv in the case of tourmaline and comes to the 

 conclusion that for that crystal the difference between 

 the isothermal and adiabatic constants is only J per 

 cent. 



Changes in Crystalline Structure due to 

 Temperature. — Describing a simple arrangement for 

 showing the alteration in the appearance, under the 

 microscope, of a polished etched metal plate when 

 heated, Herr H. Vogel, in the Zeitschrift fiir Elektro- 

 chemie, July i, 1923, makes the following assumption 

 as to the behaviour of the crystallites, of which the 

 metal is built up. If two crystallites touch one 

 another, the distance between the atoms in the 

 boundary plane of one of them will, in general, be 

 greater than in that of the other, and the forces 

 holding the atoms in these respective planes will be 

 different. When the metal is heated the first crystal 

 will grow at the expense of the other, and as this 

 takes place throughout the metal, the average size 

 of the crystallites increases. It is possible for a 

 crystallite to grow on one side and be consumed by 

 another crystallite on another, so that the relation 

 between the initial and the final structure rnay be 

 complicated. The distance between atoms in the 

 octohedron plane is greater than in the cube surfaces 

 of the lattice, and it is still greater in the rhombic 

 dodecahedron surfaces ; thus when two crystals A 

 and C touch with surfaces of the first and third kind, 

 crystal A grows ; while when A and B touch with 

 surfaces of the first and second kind, crystal B grows 

 and A is consumed. 



Chemical Analysis by X-rays. — In a paper read 

 before the Deutschen Bunsen-Gesellschaft, Dr. D. 

 Coster shows that the relations between the X - ray 

 spectra of the different elements are so simple that, in 



