May 1 8, 191 1] 



NATURE 



405 



portional to its visibility. In other words, it weights each 

 radiation according to its visibility. The voltage on a 

 tantalum lamp was varied over a wide range, and its 

 candle-power as read by thermopile and filters agreed well 

 with the readings of a photometer. Owing to the high 

 sensitiveness of the galvanometer required, the method is 

 not suitable for commercial application, except perhaps for 

 integration photometry, when a number of thermopiles 

 might be connected in series with the one galvanometer. 

 The importance of the method lies in the fact that it pro- 

 vides a satisfactory basis for heterochromatic photometry 

 independent of the Purkinje phenomenon at all intensities. 

 The author therefore proposes to use it for defining the 

 unit of light intensity. He would define the latter as that 

 source, the total intensity of radiation from which at a 

 distance of i metre after passing through his filters would 

 be ;x:ergs/sq. cm., sec. For the standard candle x should 

 be about o-8. — Prof. .'\. C. Dixon : Harmonic expansions. 



Royal Microscopical Society, April 19.— Mr. H. G. 

 Plimmer, F.R.S., in the chair.- — E. J. Spitta : Low- 

 power photomicrography, with special reference to colour- 

 ing methods. — E. J. Spitta: Report on Grayson's 

 rulings.- -E. J. Shepherd: The reappearance of the 

 nucleolus in mitosis. This was an addendum to the 

 author's previous paper, communicated in April, 1909, on 

 the disappearance of the nucleolus in mitosis. In the 

 present communication the author said that with a view 

 to ascertain how and when the nucleolus makes its re- 

 appearance, the diaster stage is the one which calls for 

 most careful study and observation. At or about the time 

 of the formation of the dispirem, and before the diasters 

 have lost their characteristic shape, a looping in the 

 chromatin is observed, the number of loops varying in 

 each daughter nucleus. It is in these loops that the 

 nucleoli will appear, but it must not be inferred that a 

 nucleolus will appear in each loop, as there are frequently 

 more loops than nucleoli. The latter make their appear- 

 ance when the division of the cell is well marked, and 

 when the interzonal fibres have generally disappeared. 

 From the results of his research, the author was of 

 opinion that the nucleolus is a product of the chromatin 

 injected into the loops by a process which can best be 

 described as a " streaming in " process. A full account 

 of the technique of staining and methods adopted, &c., 

 which have led to the above conclusion, will be found in 

 The Journal of the Royal Microscopical Society. — 

 J. IMurray : Second portion of a report from the 

 Shackleton Antarctic Expedition of 1909 on the Canadian 

 rotifera. Forty-two species (all bedlloids) were collected 

 among mosses. They included five new species, Callidina 

 asperula, C. canadensis, Mniobia ohfusicornis, M. 

 montium, and Harbrotrocha maculata. There were also 

 a number of peculiar varieties of other species. Callidina 

 asperula has since been found in Ireland by the Clare 

 Island Survey. Twenty-seven bedlloids were previously 

 recorded for the United States. Six of these occurred in 

 their collections, so that the number of bedlloids now 

 known in North .America stands at sixty-three species, but 

 n number of these were of doubtful value. .Among the 

 rarer Canadian snecies were Philodina ausfralis (Australia 

 and Canada), Callidina speciosa (British Guiana and 

 Canada), C. zickcndrahti (Russia and Canada). — Seftor 

 Domingo de Oureta : A new piece of apnnratus for 

 photomicrography, with the microscope in the inclined 

 position. 



Geological Society, April 26. — Prof. W. W. Watts, 

 F.R.S., vice-president, in the chair. — A. Wade : The 

 Llandovery and associated rocks of north-eastern Mont- 

 i^omeryshire. The area dealt with is near Welshpool, and 

 omprises part of the Severn Valley and the whole of the 

 V'ale of Guilsfield. In the succession worked out, the Ash- 

 t,'illian and the Valentian arc distinguished for, the first 

 time, while the distinction between the Wenlock and the 

 Ludlow beds is brought out by means of graptolite zon^s. 

 Ihe stratigraphiral succession is shown by traverses. The 

 district is shown to be transitional in character between 

 neighbouring districts on almost every side. The struc- 

 ture of the area is that of an anticline with " keystone " 

 faulting. The two boundary-faults of the arrh have con- 

 siderable downthrows. An account is given of the Welsh- 

 pool Dyke. The glacial geolocy of the area i^; di ■-.( ribed, 



NO. 2168, VOL. 861 



three series of deposits being observed : — (i) a high-level 

 series ; (2) a low-level series ; and (3) a stratified series. 

 The Guilsfield Valley is shown to have been occupied by 

 a glacial lake, and the reversed drainage of the Cefn-Yspn 

 Brook is shown to be connected with a " col " through 

 which the overflow water drained. — Dr. J. D. Falconer: 

 Geology of northern Nigeria. The protectorate covers an 

 area of about 255,000 square miles, over half of which 

 crystalline rocks are exposed at the surface. Hard, banded 

 gneisses of an Archaean type are intermingled with 

 quartzites, phyllites, schists, and gneisses of sedimentary 

 origin, so as to suggest that the two series, while origin- 

 ally unconformable, have been later affected by a common 

 folding and foliation along axes predominantly meridional 

 in direction. The two series have also been pierced by 

 igneous intrusions of a granitic type. Folded and faulted 

 rocks of Cretaceous age are found. These Cretaceous 

 rocks are overlain unconformably by a horizontal series of 

 sandstones, grits, conglomerates, and ironstones, which in 

 Sokoto province contains intercalations of Middle Eocene 

 limestone. Volcanic activity occurred during Tertiary 

 times, and gave rise to fields of basaltic lava in Bauchi 

 and Bornu, as also to numerous puys of trachyte, phono- 

 lite, olivine-basalt, and nepheline-basalt throughout 

 southern Bauchi, Muri, and Yola. Repeated minor 

 oscillations during the latter part of the Tertiary era 

 culminated in the elevation of the Bauchi plateau, the 

 depression of the Chad area, and the establishment of the 

 present river-system. 



Paris. 

 Academy ot Sciences, May i. — M. Armand Gautier in 

 the chair. — B. Baillaud : Remarks on the " .Annales de 

 rObservatoire de Paris " containing the observations made 

 i in 1892. — P. Villard and H. Abraham : A direct-reading 

 electrostatic voltmeter for very high pt)tentials. A 

 simplified voltmeter capable of giving accurate readings up 

 to potentials of 300,000 volts. — E. L. Bouvier : The 

 Pycnogonides of the Pourquoi Pas? This group is well 

 represented in the Antarctic regions, more species being 

 found there than in the Arctic regions. — M. Jarry- 

 Deslogres : Risumi of the physical observations of the 

 planet Mars made in the opposition 1909-10, with remarks 

 on the quality of the telescopic images in various regions. 

 The appearance and disappearance of the white polar cap 

 corresponds with a fixed Martian date. No regularity, 

 however, can be traced as regards the changes in form 

 and shade of the dark spots, which, especially in the 

 equatorial regions, do not appear to be related to the 

 seasons. No evidence could be obtained of the existence 

 of a liquid state resulting from the disappearance of the 

 white polar substance. — Jules Drach : Determination of 

 the lines of curvature of the Fresnel wave surface. — J. 

 Hadamard : The fundamental solution of partial differ- 

 ential equations of the parabolic type.— L. Godeaux : 

 Linear congruences of conies. — MM. Claude, Ferri6, and 

 Driencourt : Radio-telegraphic comparisons of chrono- 

 meters by the method of coincidences between Paris and 

 Bizerta. It has been definitely established by these experi- 

 ments that radio-telegraphic comparisons by the method of 

 coincidences are capable of giving the difference of time 

 between two chronometers 1000 miles apart, and with an 

 accuracy of at least o-oi sec. — C. Raveau : Interference 

 fringes from a linear source of light. — M. Estanave : 

 Photographs with changing colours. .A description of a 

 method of obtaining a photograph the colours of which 

 change according to the angle of observation.— M. 

 Aubert : Thermo-difTusion.— Walter Ktfniar : The displace- 

 ment of ultramicroscopic particles produced by very rapid 

 scfund shocks. A theoretical explanation of some experi- 

 mental results recently described by MM. Henri and 

 Lifschitz. — M. Pomey : The propagation on a telegraph 

 line of the current due to a constant electromotive force. — 

 Jean Perrin : The determinations of molecular magnitudes. 

 A criticism of several methods based on Stokes's law. 

 For the charge of the electron, the value 4-24 X10-" is 

 regarded as more probable than the usually accepted 

 4.8X 10-".— Jules Roux : The charge of the electron. 

 Determinations on sulphur particles lead to the value 

 417x10-"'. — .A. Blanc: The ionisation produced by phos- 

 phorus. — Georges Moreau : The ionisation of salt vapours 

 by a corpuscular radiation. — F. Loprlnce-Rlngruet : Study 



