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NATURE 



255 



subsidiary discharges, which tend to bhir the effect. The angle 

 of dispersion may be increased, or rather supplemented, by 

 placing more than one strip on the tube, distant from one 

 another by an angle of 90° or 120°. By this means the rings 

 may be made to comprise the entire circumference of the tube. 



It thus appears that the stria; are competent to cast shadow s 

 in the radiant showers issuing from the inside of the tube 

 adjacent to the tin-foil, which part acts as a negative terminal. 

 Many experiments have contributed to show th.at these radiant 

 showers, although accompaniments of the discharge, are not 

 carriers of the discharge ; and that, having once issued from 

 their source, they continue their own course irrespective of that 

 of the discharge proper. They are in fact material showers, 

 and, although not improbably charged with electricity, yet their 

 ulterior course does not appear to depend on their electrical 

 condition. Under these circumstances the simplest explanation 

 appears to be that they have been arrested by a material ob- 

 stacle, and consequently the phenomena above described may 

 be considered as furnishing an experimental proof that the striae 

 represent local aggregations of matter, and not merely special 

 electrical conditions of the gas. 



June 16. — " On Stratified Discharges. VII. Multiple Radia- 

 tions from the Negative Terminal." By William Spottiswoode, 

 P.R.S., and J. Fletcher Moulton, F.R.S. 



On examining the image of a negative terminal as traced out 

 in tubes of great exhaustion, by the phosphorescence due to 

 Crookes' radiations, we have often noticed that the image was 

 not a simple figure, but that more than one outline of the contour 

 of the terminal might be traced. From the fact of the double 

 contour having been first remnked when the terminal was of a 

 conical form, it was at first supposed that the second image 

 might be due to internal reflection, or to some property apper- 

 taining to the ed,'e of the cone. But this supposition led to no 

 satisfactory explanation of the phenomenon. 



It was however thought that, inasmuch as the two images 

 implied different systems of radiation, a magnet suitably disposed 

 might aftect them in different degrees, and thereby throw some 

 light on iheir origin. For this jiurpo-e we used a large electro- 

 magnet with its coils so coupled up as to give the two poles 

 similar polarity. By bringing tlie two poles together, inclined 

 at a moderate angle, a single pole and a field of great magnetic 

 strength was produced. 



The tube was then placed in the plane containing the axis of 

 the two poles, and in the direction of a line bisecting their 

 directions. The tubes first used were of great exhaustion, and 

 were placed sometimes with the positive, sometimes with the 

 negative terminal towards the magnet. When the tube was placed 

 m a comparatively weak part of the field the two images of the cone 

 were seen in their usual positions relatively to each other, except 

 that they were slightly more separated. But as the tube was 

 brought gradually into a stronger part of the field the two images 

 liecame further separated, and by degrees a third, a fourth, and 

 even more images were brought out on the side of the tube. In 

 one tube of very high exhaustion, for which we are indebted to 

 Mr. Crookes, as many as eight images became visible. 



We have then, as an experimental fact, a series of images, 

 each formed by a system of rays issuing from the surface of the 

 negative terminal. The images being distinct, the system of rays 

 mu>t be distinct also. Now, as it seems hardly possible to 

 imagine that, from every point of a surface, there can issue at 

 one and the same instant of time a variety of systems of radia- 

 tions, each system ranging over a finite angular distance, and 

 each differently directed in space, we are driven to the conclusion 

 that these radiations must have issued successively and not simul- 

 taneously from the terminal. In other w'ords, the various images 

 are formed in succession. Now, the entire series of images are 

 present whenever a discharge passes through the tube ; and when 

 a "continuous" discharge (such as that from a Holtz machine) 

 is passing, they are all as steady and as persistent as are any other 

 features of the discharge. From this it follows that the radia- 

 tions are not a continuous phenomenon, but that they are com- 

 posed of a recurrent series of discharges, each having its own 

 angular range, and its own direction in space ; and as the elec- 

 tricity, w-hich is the motive powder, and the metallic terminal, 

 which is the directing machinery, are the saire in kind for each 

 image, we are led to the conclusion that the positions of the 

 images are determined by the force with which the radiations are 

 projected. In fact, we understand that the various images are 

 due to a succession of discrete discharges of successively 

 diminishing strength. 



The phenomenon of multiple images of the negative terminal 

 as explained above has an important bearing on the nature of 

 electrical discharges in vacuum tubes. For, if the phosphorising 

 radiation consists of a recurring series of discrete discharges, the 

 radiation in each series, and a fortiori the radiation as a whole, 

 is discontinuous ; and consequently the electrical discharge, to 

 which it is due, must itself be discontinuous or '"disruptive." 

 We appear, therefore, in these phenomena to have an experi- 

 mental proof, independent of and in addition to those adduced 

 by Mr. be La Rue and others, of a fundamental point in the 

 theory of these discharges, namely, their disruptive character. 



Geological Society, June S.— R. Etheridge, F.R.S., pre- 

 sident, in the chair. — The meeting was made a special general 

 meeting for the election of a Member of the Council in the room 

 of the late Sir P. de Malp.asGrey-Egerton, Bart., M.P., F. R.S., 

 F.G.S. — The President announced that the late Sir Philip Eger- 

 ton had bequeathed to the Society all the original drawings made 

 from specimens in his collection for the illustration of Prof. 

 Agassiz's works on Fossil Fishes. The .Society had long pos- 

 sessed tlie drawings made for the same purpose from the 

 Earl of Ellesmere's collection, and some years ago the Earl 

 of Enniskillen presented those which had been prepared 

 from specimens in his possession. .Sir Philip Egerton's kind 

 bequest would complete this interesting series. — Sir John Lub- 

 bock, Bart., M.P., F.R.S., was elected a new Member 

 of Council. Messrs. Grenville A. J. Cole and J. L. Roberti 

 were elected Fellows, and II Commendatore Quintino Sella 

 of Rome a Foreign Member of the Society. — The following 

 communications were read : — The reptile-fauna of the Gosau 

 formation, preserved in the Geological Museum of the University 

 of Vienna, by Prof. H. G. Seeley, F.R.S., with a note on the 

 geological horizon of the fossils, by Edward Suess, F.M.G.S. 

 The collection of reptiles described in this paper was obtained 

 at Neue Welt, near "Wiener Neustadt, by tunnelling into the 

 freshwater deposits which there yield coal. A part of the col- 

 lection was described by Dr. Bunzel in 1S71 ; but the author': 

 interpretation of the fossils rendered a re-examination of the 

 whole collection necessary. All the species hitherto discovered 

 are new, and, with the exception of those referred to Crocodilus, 

 Megalosaurus, Ornithochirus, and Emys, are placed in nev 

 genera. Nearly all the bones are more or less imperfect. The 

 Iguanodon Stussii, of Bunzel, was refened to a new genus, 

 Mochlodoii, characterised by the straight antericr end of th( 

 ramus of the lower jaw and by the vertical bar in the middle of 

 the teeth of the lower jaw. There appear to be two teeth in the 

 ramus. The tooth referred to the upper jaw has several unifom' 

 parallel vertical bars. A small parietal bone, referred by Bunzel 

 to a lizard, is considered by the author to belong probably to the 

 same species, and, with some doubt, he associated with it the 

 articular end of a small scapula. Bunzel's Slrutlmsaurus 

 Aiistriacits was re-described by the author, who indicated that 

 the bones of the base of the brain-case, regarded by -Bunzel as 

 the quadrate bones, really belong to the occipital region, which 

 necessitates a difierent interpretation. The foramina along the 

 base of the skull were also described as presenting one of the 

 characteristics of the Dinosaurian order. The base of the skull 

 of AcanilwpholU horridus was described to show its relation to 

 the above type, with the view of demonstrating its Scelidosaurian 

 afiinities. The greater part of the remains were referred by the 

 author to a new genus, Craticomus : some of these had been 

 figured by llunzel as "Crocodili ambigui,"and others as belong- 

 ing to Scdidosaiiriis, and to a new Lacertilian genus, Danutno- 

 saiiriis. To Crati€0)iius he referred mandibles, teeth, vertebra; 

 from all parts of the column except the sacrum, dermal armour, 

 and the chief bones of the limbs. Two species were distin- 

 guished, C. Paidowitschii and C. lepidophorus. The former, 

 which is much the larger, was named in honour of M. Paulo- 

 witsch, who voluntarily superintended the work at the Neue 

 Welt. The author stated that he regarded these animals as 

 carnivorous, and that, unlike the typical Wealden Dinosaurs, 

 they were not kangaroo-like in habit, but had strongly developed 

 fore limbs, as indicated in the proposed generic name. Two 

 teelh-'belonging to Mcgalosaiirus were described as representing 

 a new species, M. Pannoni-msis, characterised by the crown 

 being shorter and broader than in previously described forms. 

 A fragment, regarded by Bunzel as the thoracic rib of a lizard, 

 was interpreted as the distal end of the femur of a Dinosaur, and 

 named Oniit/iomerus gracilis. The lower jaw, described by 

 Bunzel as Crocodilus carcharidats, of which a maxillary bone 

 also occurs, was made the basis of a new genus, Doratodoit, 



