576 



NATURE 



[April 1 1 , I 



and Wiirtemberg, but also in Baden, keeping the observations 

 of lightning separate from those of mere rain-storms : this seemed 

 to be necessary, not only inasmuch as von Bezold did not lake 

 any account of lightning, but also because the occurrence of light- 

 ning at the time of new moon, or during the last quarter of the 

 moon, might give rise to apparent maxima resulting from purely 

 optical causes. He found that the storms possess a periodicity of 

 29 days, which include three maxima, the chief of these being in 

 the last half-quarter, the next at new moon, and the least at full 

 moon. No physical explanation, or even any idea of any con- 

 nection between the storms and the phases of the moon, can 

 at present be given. — Dr. Assmann gave an account of a 

 phenomenon which had been observed on the trees in the Thier- 

 garten as a result of the recent heavy snow-fall. The masses of 

 snow which were piled up high on the branches of the trees had 

 slipped down round their sides and hung down like curtains ; 

 they possessed a not inconsiderable consistency and glacier-like 

 structure. The superficial thawing which occurred daily about 

 midday had contributed largely to bring about the modification 

 which the snow had undergone. 



Physiological Society, March 15. — Prof, du Bois-Reymond, 

 President, in the chair.— Dr. Eenda spoke on multinuclear mam- 

 malian spermatozoa, and refuted a number of objections which 

 had been raised to his views on spermatogenesis. — Prof. Gad 

 gave an account of experiments which Dr. Piotrowski had made 

 under his direction, on the difference between the conducting 

 power of nerves and their irritability. It was known that under 

 certain conditions, as, for instance, when a nerve is dying or is 

 surrounded by an atmosphere of carbonic acid gas, its power of 

 conducting impulses shows no change, while at the same time the 

 irritability of that part which is surrounded by the gas has dis- 

 appeared. After confirming the above by renewed experiments. 

 Dr. Piotrowski found that when he surrounded a small stretch of 

 the sciatic nerve with alcohol vapour he obtained a result exactly 

 the reverse to that observed with carbonic acid gas : the nerve 

 was irritable, but could no longer convey impulses coming from 

 its central end. Irritability and conducting power were tested, 

 not only by muscular contractions, but also by the negative varia- 

 tion at the peripheral end of the nerve. Three distinct causes 

 might be assumed for the difference between irritability and con- 

 ducting power which had been experimentally proved as above. 

 In the first place, irritability and conducting power might be two 

 totally distinct properties of a nerve. But this view must be dis- 

 missed, inasmuch as the only possible way of conceiving the 

 propagation of an impulse is to suppose that the impulse is trans- 

 mitted from one transverse section of the nerve to another, so 

 that the stimulation of one section acts as a stimulus to the rest. 

 In the second place, it might be supposed that the electrical re- 

 sistance of the nerve-sheath and medullary-sheath had been in- 

 creased, so that the stimulus, which was applied from the exterior, 

 could not overcome this increased resistance, while at the same 

 time the conducting power of the axis-cylinder remained un- 

 changed. But this view is untenable in face of the fact that 

 alcohol vapour increases the irritability of a nerve but lessens its 

 conducting power. And it is still further opposed by an ex- 

 periment on the olfactory nerve of the pike. This nerve possesses 

 scarcely any sheath, or at most an extremely thin one, and still 

 it behaved exactly as does a sciatic nerve when surrounded by car- 

 bonic acid gas. Finally, mechairical stimuli were just as efficient 

 as electrical, and in this case the resistance of the sheath does not 

 affect the question. A third possible explanation was that 

 nerves possess not only a longitudinal, but also a transverse 

 irritability, and that the latter is diminished by the COo, and 

 increased by the alcohol vapour. This last explanation was also 

 rendered probable by an experiment in which the heightened 

 irritability under exposure to alcohol vapour was still further in- 

 creased when the current used for stimulation was led through 

 the nerve at right angles to its length by means of wide elec- 

 trodes instead of by means of the wire electrodes usually em- 

 ployed, in which latter case a small longitudinal stretch of the 

 nerve is included between the points of the electrodes. The 

 speaker therefore regards it as proved that the irritability of a 

 nerve can be diminished by the action of CO2 without its con- 

 ducting power being simultaneously affected. Further, that by 

 means of alcohol vapour the irritability may be increased, while 

 the conducting power is at the same time considerably dimin- 

 ished, and that nerves possess a distinct transverse irritability. 

 The speaker also regarded it as extremely probable that the effect 

 of CO2 and alcohol vapour is different upon the transverse and 

 longitudinal conducting powers of a nerve. 



Vienna. 



Imperial Academy of Sciences, February 7. — The Secre- 

 tary read a letter by Dr. Ludolf Griesebach on his travels in Turkis- 

 tan, describing the geology of the environs of Ghazni. — The 

 following papers were read : — On the retinal image of the insect's 

 eye, by Prof. S. Exner. — On the orbit of Winnecke's comet in 

 the years 1858-86, by E. von Haerdtl. — On the relation of 

 atmospheric pressure to electricity (sealed), by T. Altschul. 



February 17. — The following papers were read: — On some 

 derivatives of cyanamide, by A. Smolka and A. Friedrich. — On 

 morphine, by Zd. H. Skraup and Dr. Wiegmann. — On the 

 definitive determination of the plane of polarization, by the late 

 L. Kudelka. — On an anomaly of MendeleefTs periodic system 

 (sealed), by B. Brauner. — On marine Hydrachnida, with some 

 remarks on Midea (Bruz), by R. von Schaub. — On the passage 

 of electricity through bad conductors, by H. Koller. 



BOOKS, PAMPHLETS, and SERIALS RECEIVED. 



Egeson's Weather System ofSunspot Causality : Charles Egeson (Sydney, 

 Turner and Henderson). — The Chemistry of Photography : R. Meldola 

 (Macmillan). — First and Fundamental Truths: J. McCosh (Macmillan). — 

 British Dogs, No. 30: H. Dalziel (U. Gill).— The Dentists' Register, 1889 

 (Spottiswoode). — The Medical Register, iSSgCSpottiswoode). — A Treatise on 

 Manures : A. B. Griffiths (Whittaker). — Argentine Ornithology, vol. ii. : P. 

 L. Sclater and W. H. Hudson (Porter). — Encyclopsedia Britannica, ninth 

 edition, index (Edinburgh, Black). — By Leafy Ways : F. A. Knight (Stock). 

 — An Elementary Text-book of Applied Mechanics: D. A. Low (Blackie). — 

 Journal of the Scottish Meteorological Society, third series, No. s (Black- 

 wood). — Deutsche Ueberseeische Meteorologische Beobachtungen, Gesam- 

 melt und Herausgegeben von der Deutschen Seewarte, Heft 2 (Berlin).-— 

 Journal of the Chemical Society, April (Gurney and Jackson). — Geological 

 Magazine, April (Triibner). — Mind, April (Williams and Norgate). — Himmel 

 und Erde, April (Berlin). 



CONTENTS. PAGE 



British Uredineae and Ustilagineae 553 



Thomas Andrews . . 554 



Mach's "History of Mechanics" 556 



Our Book Shelf:— 



Dove : " Das Klimades ausser-tropischen Siidafrika" 556 



" Chambers's Encyclopaedia " 557 



Swinton : "The Elementary Principles of Electric 



Lighting" 557 



Fayrer : " The Natural History and Epidemiology of 



Cholera" 557 



Letters to the Editor:— 



Halo and Mock Suns.— James C. McConnel ... 557 

 On the Connection between Earth Currents and 



Changes in Solar Activity. — Henry Crew .... 557 

 Hertz's Equations in the Field of a Rectilinear 



Vibrator.— Rev. H. W. Watson 558 



Early History of Lightning-Conductors. — Prof. Karl 



Pearson 558 



The Satellite of Procyon.— Isaac W. Ward ... 558 

 Factors of Numbers. — Lieut. -Colonel Allan Cun- 

 ningham, R.E 559 



The Geographical Results of Mr. Stanley's Expedi- 

 tion. ( With a Map) 560 



A New Permian Rhynchocephalian Reptile. By G. 



A. Boulenger 562 



The Spectrum of the Rings of Saturn 564 



On the Speed of the Electric Transmission of 

 Signals through Submarine Cables and Land 



Wires. By General J. T. Walker, F.R.S 564 



Notes 565 



Our Astronomical Column : — 



The Luminosity of Venus . . , 567 



The Spectra of R Leonis and R Hydrae 567 



The Sun-spot Minimum 567 



Discovery of a New Comet • . . . . 567 



Observations of Variable Stars in 1888 568 



Astronomical Phenomena for the Week 1889 



April 14-20 568 



Geographical Notes 5^8 



Biological Notes : — 



The Rattle of the Rattlesnake 569 



A New Species of Laminaria 569 



The Envelopes in Nostocacese 569 



The Scottish Meteorological Society 569 



Two-nosed Catenaries 57o 



Scientific Serials ,, ,' 57i 



Societies and Academies 57 1 



Books, Pamphlets, and Serials Received 576 



