May 27, 1S97] 



NA TURE 



spectrum lines by the action of a magnetic field on the source of 

 light : Prof. Oliver Lodge, F.R.S. 



Commensalism amongst marine animals : the Marine Biological 

 Association. 



Experiments on the transmutation of sound vibrations : Mr. J. 

 (Icold. 



Kxamples of animal-forms peculiar to Lake Tanganyika : Mr. 

 1. E. S. Moore. 



The Tsetse fly and the parasite of Tsetse fly-disease, or 

 \gana : Dr. A. A. Kanthack, Mr. W. F. H. Blandford, and Mr. 

 HE. Durham. 



(i) Egg oi .-Epyortits maximus (Grandidier), Madagascar,: 

 (2) egg of African ostrich for comparison of sizfe ; (3) photo- 

 graph of a fossil frog (Discoglossus Troscheli, Meyer sp.) from 

 Ihe lignite (Miocene) of Rott, near Bonn, and sciagraph of a 

 recent frog of the same genus (Discoglossus picttts, Otth), for 

 comparison. By Messrs. James Green and James H. Gardiner : 

 Dr. Woodward, F.R.S. , on behalf of Mr. R. Damon. 



Ceraierpeton Gaivani, Huxley, coal measures, Kilkenny, 

 Ireland : Dr. Woodward, F.R.S., for Mr. J. G. Robertson, of 

 Dublin. 



( I) Living specimens of the British Mymaridae (egg parasites), 



rrestrial and aquatic ; (2) mounted specimens of newly-dis- 



vered genera. Mounted specimens of newly-discovered male 

 1 restwichia : Mr. F. Enock. 



(I) Specimens of Lepidoptera altered by temperature experi- 

 ments, and reared by the exhibitor ; (2) some of the results of 

 crossings carried out by the exhibitor : Dr. M. Standfuss, of 

 Zurich. 



Examples of alteration of insects by temperature applied in 

 the pupal stage : Mr. F. Merrifield. 



Some examples of geographical distribution among the micro- 

 Lepidoptera, with specimens from dififerent regions, and coloured 

 maps : Lord Walsingham, F.R.S. 



Blood corpuscles of some invertebrate animals. Digestive 

 inland of Ostrea : Dr. C. A. MacMunn. 



A rotating mirror, specially made to the order of exhibitor 

 liy the Cambridge Instrument Co. : Sir David Salomons, Bart. 



A rowing indicator, giving continuous record : Mr. F. C. 

 Atkinson. 



A new pocket mercurial standard barometer : Prof. J. Nor- 

 man Collie, F.R.S., and Captain H. H. P. Deasy. 



An apparatus for investigating the influence of proximity of 

 substances on voltaic action : Dr. Gore, F.R.S. 



Micrometer for microscopic measurement of large objects. 

 Manufactured by the Cambridge Scientific Instrument Co. : 

 I'rof. W. F. R. Weldon, F.R.S. 



Earth thermometer. A simple apparatus for the determin- 

 ation of earth temperatures : Mr. E. H. Griffiths, F.R.S. 



Exjjeriments illustrating a new method of controlling the 

 electric arc in its application to photo-micrography: Mr. T. A. B. 

 Carver and Mr. J. E. Barnard. 



Kamm's " Zerograph," or "Printing Telegraph System": 

 Mr. L. Kamni. 



New phototheodolite, designed by Mr. J. Bridges-Lee : Mr. 

 Caselia. 



The following demonstrations, with experiments and lantern 

 illustrations, took place in the meeting-room : — 



Experimental demonstration of " some electric and mechanical 

 analogues": Prof. W. E. Ayrton, F.R.S. 



Lantern-slides from micro-photographs, illustrating nuclear 

 division in animal and vegetable cells: Prof.'J. :B. Farmer. 

 Slides were shown illustrating the process of fertilisation and 

 segmentation of the egg in Ascaris megalocephala, and in Fttcus 

 vesiculosus. 



INFLUENCE OF RONTGEN RAYS UPON 

 ELECTRICAL CONDUCTIVITY.^ 



TN a note read on March i in the Royal Society of Edinburgh, 

 Lord Kelvin, Drs. Beattie, and Smolan treat of the influ- 

 ence of the Rontgen rays on the conductivity of air, paraffin, 

 and glass (Nature, vol. Iv. pp. 498-99). After careful experi- 

 ments, made with different potentials, they conclude that no 

 perceptible increase of the conductivity of paraffin and glass is 



1 Experiments published May, June, July i8q6, proving^ that solid and 

 liquid insulators retain their insulating powers under the influence of the 

 Rentgen rays. By Prof. Villari. Communicated by Lord Kelvin. 



NO. 1439, VOL. 56] 



produced on them by the action of the X-rays. On the contrary, 

 Messrs. J. J. Thomson and M'Clelland have thought, after their 

 experiments, that paraffin and glass, submitted to the X-rays, 

 increase conductivity. I had employed myself in the same 

 question some time before, and I have explained the results of 

 my researches in two notes presented to the Royal Academy of 

 Naples on May 9 and July 4, 1896, and in a third note pre- 

 sented to the Royal Academy of the Lincei in Rome on June 6, 

 1896. This last note begins with the following words : — 



" My first idea was to study whether the X-rays, crossing a 

 dielectric, could render it conductor, so as to facilitate across it 

 the discharge of an electrified body. In these researches of 

 mine I employed, as a dielectric, some paraflin because, besides 

 its being one of the best insulators, it is also very transparent to 

 the X-rays." 



The results set forth in those three notes may be thus shortly 

 re-stated. 



The discharge of a conductor in the air, provoked by the X- 

 rays, seems to take place by convection or transport ; so to say 

 by an electric dance of the particles in the air, roused by radiation. 

 Righi's experiments lead likewise to a similar interpretation. 



The discharge of the conductor becomes slower when the sur- 

 face exposed to air is diminished — that is to say, when a portiorj 

 of it is covered with paraffin. 



A conductor, loaded with electricity and narrowly surrounded 

 by a wrapper of paraffin, loses, by a first action of the X-rays, a 

 small part of its discharge, and in the following times, after 

 having been freshly charged to its primitive force, it always loses 

 less, so that at the third, fourth, or fifth experiment the dis- 

 charge is imperceptible or next to nothing. Therefore paraffin, 

 under the action of the X-rays, does not gain in conductivity. 



India-rubber behaves almost in the sam£ manner as paraffin. 



If the conductor is surrounded first by air and further out by a 

 tube of paraffin, the conductor excited by the X-rays discharges 

 itself, at first rapidly enough ; but, soon after, the discharge 

 proceeds, to the last, very slowly. As usual, electricity, carried 

 by air, soon loads the sides of the tube, and then disperses 

 itself with difficulty. 



Electricity, scattered from the body, submitted to the action 

 of the rays, can join itself again on a tube of paraffin, or of insu- 

 lated metals, surrounding the discharging body. This electricity, 

 gathered up on a tube, can be directly observed with an electro- 

 scope provided with dry piles, and is found, as is to be expected, 

 of the same nature as that of the body itself. 



Insulating liquids (turpentine oil, vaseline, Venetian turpen- 

 tine, and petroleum) were also examined by me, and they be- 

 haved almost in the same manner as paraftin. An electrified 

 conductor submerged in one of these liquids (vaseline oil is the 

 best of all), under the action of the X-rays, discharges itself at 

 first rapidly, but soon after the discharge stops almost entirely. 



Lastly, the conductive property of the gases, crossed by the 

 X-rays, increases with their density, and may be ranged in the 

 following order : — 



Hydrogen, lighting gas, air, carbonic anhydride, and vapours 

 of ether or carbonic sulphur. 



The results, relative to the first four gases, agree with those 

 already given by Righi. 



THE CHEMISTRY OF THE HOTTEST STARS. 



AT a discussion meeting of the Royal Society, held some two 

 months ago, a paper was read by Mr. J. Norman Lockyer, 

 C.B., F.R.S., under the above title. This has recently been 

 published, and we reproduce the general conclusions. 



(i) In a mixture of vapours at a particular temjjerature, a 

 vapour which is not present in sufficient quantity to show all 

 the lines of its spectrum will be represented by the lines which 

 are longest in its spectrum at the particular temperature in 

 question. 



Only some of the short lines in metallic spectra represent the 

 effects of high temperature. 



(2) Some of the substances which have been investigated, in- 

 cluding iron, calcium, and magnesium, have probably a definite 

 spectrum, consisting of a few lines, which can only be com- 

 pletely produced at a temperature higher than any which is at 

 present available in laboratory experiments. The lines con- 

 stituting the new spectra are those which either only appear in 

 the spark spectrum, or are lengthened in passing from the arc to 

 the spark. Such lines are termed enhanced lines. 



