January 25, 1900] 



NA TURE 



31 



The minimum seems to have been about 28"i inches ; at Camden 

 Square, London, where the lowest reading was 28 247 inches. 

 The only lower readings there since 1858 have been: 28-332 

 inches on January 24, 1872 ; 28364 inches on December 4, 

 1876; and 28295 inches on December 9, 1886.— Severe frost 

 in December 1899. A table shows the number of shade minima 

 below 15°. Near Hereford a temperature of - 2° was recorded 

 on the 15th in a screen of the Stevenson pattern. At Lyme 

 Regis, Dorset, a correspondent writes that some soda-water 

 bottles which were opened on the golf links all instantly froze ; 

 before being opened they were perfectly fluid and free from ice. 



SOCIETIES AND ACADEMIES. 



London. 



Royal Society, December 7, i%gg.~'' Polytremacis and 

 the Ancestry of the HelioporidiS." By J. W. Gregory, D.Sc. 

 Communicated by Prof. Lankester, F. R.S. 



The recent blue coral Heliopora presents striking resemblances 

 in structure to the pal.^ozoic Helioliles. All the earlier writers 

 on corals accordingly regarded the two genera as intimately 

 allied But some later authorities consider the resemblances as 

 accidental, and that the corals have no special aflinities. Thus, 

 according to F. Bernard, Heliopora and Helioliles belong to dis- 

 tinct subphyla. Lindstrom admits only one species of Heliopora, 

 and regards the genus as quite isolated, as essentially distinct 

 in structure from Helioliles, and as further separated from the 

 latter by " the total absence of all connecting links from the end 

 of the middle Devonian to the recent times." The author, 

 however, considers that the original view of the close affinity of 

 Heliopora and Helioliles is correct, that the two genera are 

 essentially similar in structure, and that they are linked by a 

 series of eocene and cretaceous corals. Amongst these fossils is 

 the genus Polylremacis, which is redescribed, and a new species 

 of Heliopora from the cretaceous of Somaliland. It is suggested 

 that Heliopora has descended from the palaeozoic Heliolitidae by 

 degeneration in size and increase in number of the coenenchymal 

 caeca. 



"On the Association of Attributes in Statistics, with 

 Examples from the Material of the Childhood Society, &c." 

 By G. Udny Yule. Communicated by Karl Pearson, F. R. S. 



Geological Society, January lo.—W. Whitaker, F.R.S., 

 President, in the chair. — On a particular form of surface, the 

 result of glacial and subaerial erosion, seen on Loch Lochy and 

 elsewhere, by Dr. W. T. Blanford, F. R S. This form of sur- 

 face, first noticed by the author on Lake Como, was afterwards 

 observed in the Great Glen of Scotland and in British Columbia. 

 It consists of an almost even plane sloping at a moderate or 

 high angle, and cut at intervals by small ravines or channels. 

 The sides of the Great Glen have been planed by glacier-action 

 to a greater extent than usual, and between Loch Lochy and 

 Loch Oich, near Laggan, the sides of the Glen have a regular 

 and flat slope of over 35° up to about 1000 feet above sealevel. 

 Numerous stream-cut channels draining down this slope are, on 

 an average, not more than 10 to 15 feet deep, but some quite ex- 

 ceptional examples may be 50 feet deep ; these channels occupy 

 less than a fourth of the surface. In addition there are larger 

 glens which, although they run out into shallow ravines where 

 they cut the sloping side of the Great Glen, are frequently 500 

 feet in depth among the hills. If these were ordinary stream- 

 valleys before the Glacial Period, the cutting away of the ridges 

 separating them to the extent of at least 250 or 300 feet must 

 be attributed to glacial erosion on the sides of the Great Glen. 

 The erosion of the small ravines in the glacial slope must have 

 been effected by streams in post-Glacial tiines, and the measure- 

 ment of their rate of erosion might be expected to throw light 

 on the amount of time which has elapsed since the Glacial 

 Period in this district. "The general eff'ect produced by the 

 whole evidence is ... the small amount of denudation that has 

 taken place since the Great Ice Age, and the necessary deduc- 

 tion that no great period of time, measured in years, can have 

 elapsed between the Glacial Epoch and the present day." — On 

 the geology of Northern Anglesey (Part II.), by C. A. Matley. 

 — The formation of dendrites, by A. Octavius Watkins. If two 

 plane-surfaces be separated by a film of suitable plastic material, 

 and one surface be rotated slowly on the other through a small 

 arc, the plastic material collects into branching forms similar 

 to the structure of dendrites. The dendritic form starts from 



NO. 1578, VOL. 61] 



the part farthest from the axi^ and the flow of material is from 

 the smaller to the larger branches, the smaller uniting to form 

 the larger. The author explains dendritic structure by the 

 formation of a fissure in rock which becomes filled with a thin 

 film of dendritic material ; if the fissure is slowly widened, the 

 dendrite starts where the widening commences, coinciding den- 

 drites being formed on each wall. 



Royal Meteorological Society, January 17. — Annual 

 Meeting. — Mr. F. C. Bayard, President, in the chair. — In his 

 presidential address, Mr. Bayard discussed the meteorological 

 observations made at the Royal Observatory, Greenwich, during 

 the fifty-one years 1848- 1898, and brought out in a novel way 

 many interesting features in the variability of the various observ- 

 ations of the barometer, maximum and minimum temperatures, 

 relative humidity, direction of the wind and rainfall. These 

 were shown in a diagrammatic form on the screen by means 

 of a number of lantern slides. The address was also illustrated 

 by various views of the Royal Observatory and of the instru- 

 ments employed.— Mr. G. J. Symons, F.R.S., was elected 

 President for the ensuing year. 



Paris. 



Academy of Sciences, January 15 — M. Maurice Levy in 

 the chair. — On the distribution of the abnormal residues of a 

 function, by M. H. Pade — On the reduction of an algebraical 

 problem, by M. J. Ptaszycki. — Determination of the invariants^ 

 attached to the group Gjes of M. Klein, by M. A. Boulanger. 

 — Vector fields and fields of force. Reciprocal action of scalar 

 and vectorial masses. — Localised energy, by M. Andre Broca. 

 — On the distribution of potential in a heterogeneous medium,, 

 by M. A. A. Petrovsky. — On the co-volume in the characteristic 

 equation of fluids, by M. Daniel Berthelot. A comparison of 

 the experimental isotherms for carbon bisulphide, ethyl chloride,- 

 carbon dioxide and ethylene with various modifications of the 

 Van der Waals formula. If the co-volume b be regarded as a 

 function of the temperature, the Van der Waals equation can- 

 be made to represent well the liquid state. The formula pro- 

 posed by the author is (Jt = (^cJ ^ + o'3 (q^ - i ) . where 



3t is the co-volume at T, b^ that at the critical temperature, T^. 

 — On the mechanism of hearing, by M. Firmin Larroque. For a 

 simple sound, whether the wave phases are concordant or not, the 

 centre of perception receives two transmitted impressions to- 

 gether, there being no interference in any case. For two simple 

 or complex sounds, two corresponding impressions are received 

 by the centre of perception, there being neither beats nor re- 

 sultants, the two ears being acoustically distinct. — The per- 

 manent modifications of metallic wires and the variation of 

 their electrical resistance, by M. H. Chevallier. If the resist- 

 ance of a wire is R at a temperature T,,, then heated to T, and 

 again measured at To, in general, the resistance R' last measured 

 will be different from R. The phenomenon appears to be due 

 to a tempering effect, and is most clearly marked with metals^ 

 and alloys that have not been hardened. The effect is very 

 marked with ordinary platinum-silver wire. — On the Hall 

 phenomenon and thermomagnetic currents, by M. G. Moureau. 

 The thermomagnetic currents discovered by Nernst and Ettings- 

 hausen in 1886 to exist in a thin metallic plate placed in a 

 magnetic field normally to the lines of force and traversed by- 

 a heat current. Several attempts have been made to explaia 

 these phenomena, by hypotheses resting upon numerous ar- 

 bitrary assumptions. The author now shows that these re- 

 sults are an immediate consequence of the Hall effect, 

 the values calculated from this point of view agreeing 

 extremely well with the experimental numbers, except in the 

 cases of nickel and cobalt, which require further investigation.- 

 —On the discharge of electrified bodies and the formation of 

 ozone, by M. P. Villard. The author concludes from his ex- 

 periments that in ordinary air incandescent bodies may emit 

 kathode rays comparable to the Lenard rays, but of very low 

 voltage. If this is the case, several distinct phenomena can be 

 explained ; the power of discharging electrified bodies possessed 

 by flame, incandescent bodies and phosphorus; the discharge by 

 ultra-violet light, the production of ozone by flames, incan- 

 descent bodies, oxidation of phosphorus, electric sparks, and by 

 radium. — On a method of measuring the velocity of the Rontgen 

 rays, by M. Bernard Brunhes. The ordinary methods of 

 measuring the velocity of light cannot be used with the X-rays 

 since they are not reflected, but by applying the discovery of M. 



