262 



NATURE 



rjuLY 15, 1897 



notwithstanding the fact that the result of superposing two 

 nearly equal effects due to light of the same intensity— or 

 nearly so — had been found not to be equal to, but less than that 

 due to light of double the intensity acting for half the time. If 

 the resultant effect were equal to the sum of the separate ones, 

 the effect caused by the change of absorption would have been 

 still more marked. 



The effect can also be shown by the photometer, for if o = fi, 



taking the maximum value of a = 0"48, the ratio = o"32, 



I +<* 

 and instead of obtaining equality when the photometer is 

 adjusted for this value the difference is most marked. 



"On the Relative Behaviour of the H and K lines of the 

 Spectrum of Calcium." By William Huggins, D.C.L., LL.D., 

 F.R.S., and Mrs. Iluggins. 



The problem before us was to find out by experiments in the 

 laboratory, under what conditions the lines of calcium other 

 than the lines H and K, and in particular the strong blue line 

 at 4226 "9, were so greatly enfeebled relatively to H and K, that 

 they became quite insignificant, or even disappeared altogether 

 from the spectrum, leaving the very simple spectrum of the two 

 lines H and K, or nearly so. 



It was suggested to us by the known rarer state of the gases 

 in the regions above the photosphere, as well as by my long ex- 

 perience with the behaviour of calcium fti comparison spectra, 

 that the modifications of the calcium spectrum which we were 

 seeking, would be likely to show themselves under conditions of 

 greatly reduced density of the calcium vapour. 



For obvious reasons we elected to use throughout the experi- 

 ments a spark of very small intensity. 



Our expectations were completely confirmed. Under the 

 conditions {a) of greatest density of the calcium vapour, when 

 metallic calcium was employed, the blue line was as strong and 

 possessed the same diffuse character as H and K. 



As the density of calcium was reduced, the lines were not 

 found to be equally enfeebled, but, on the contrary, the blue 

 line and the greater number of the lines were increasingly re- 

 duced in intensity relatively to H and K, until at last with the 

 twice washed electrodes (rf) the spectrum was simplified to the 

 <:onditioh usually existing in the prominences, in which H and 

 K only are present. 



A more precise statement of the changes of relative intensity 

 as they are presented in the photographs on the plates are given 

 in the paper. 



The only condition which was varied during this set of ex- 

 periments was the amount or density of the calcium vapour. 

 The changes of relative intensity, and the modifications of the 

 calcium spectrum produced thereby, correspond closely to the 

 behaviour of calcium at different levels near the sun's limb, and 

 in the atmospheres of stars of different orders. There can 

 remain little doubt that the true interpretation of the changes in 

 appearance of the calcium lines in the celestial bodies is to be 

 found in the different states of density of the celestial gases from 

 which the lines are emitted or by which they are absorbed. 



In the modifications of the calcium spectrum arising from 

 variations in the relative intensities of the lines which have 

 been discussed in this paper, and which correspond to those 

 observed in the celestial bodies, there does not appear to us 

 any reason for assuming, much less any direct evidence in 

 favour of, a true dissociation of calcium, that is, of its reso- 

 lution into chemically different kinds of matter, 



A letter from Prof. Liveing is added, which contains an 

 account of early experiments on the spectrum of calcium 

 which support, by a different method of working, the con- 

 clusions of our paper ; and seem to show the possible occur- 

 rence of the line 11 without K. In our experiments both H 

 and K were always present, K being stronger than H, as is 

 the case in the photographs of the prominences by Hale, 

 and by Deslandres. 



" Stress and other Effects produced in Resin and in a Viscid 

 ■Compound of Resin and Oil by Electrification." By J. W. • 

 Swan, F.R.S. 



In this paper are described the stress and other effects pro- 

 •duced by non-luminous electrical discharges on a viscid mixture 

 -of resin and oil. Wires from the discharging terminals of an 

 induction coil or Wimshurst machine were led, one above and 

 the other below a glass dish containing the resin mixture. The 

 terminal above the resin surface was usually a point, ball, or 

 -disc, and the one below was a disc, forming a support for the 



NO. 1446, VOL. 56] 



dish of resin. The discharging arms of the coil were used as a 

 spark gap. The spark, 25 to 50 mm. long, always passed at 

 the spark gap, the terminals above the resin being so adjusted 

 that the resistance to discharge was slightly greater there than at 

 the spark gap. When the upper terminal is a ball, and connected 

 to the -f electrode, then on a spark passing at the spark gap there 

 is produced on the surface of the viscous mixture a star-shaped 

 figure, formed of deeply-furrowed, closely-clustered, outward- 

 branching rays, extending from a circular frill near the centre 

 to the margin of the dish. The figure gradually dies down, and 

 when the surface is smooth it may be produced again and again. 



If the terminal above the resin surface be made — instead 

 of -f , then on a spark passing at the spark gap, a figure char- 

 acteristic of the ~ discharge is produced. This figure is much 

 smaller and weaker than the -f one ; most frequently it con- 

 sists of a circular band or ring, more or less indented in out- 

 line, enclosing leaf-like rays which tend towards the centre. 

 These are relatively broader and less branching than the -f 

 rays, and are in relief, while the -J- rays are below the plane 

 of the surface. When the electrification is strong, the ring 

 enclosing the rays stands up as a frill in considerable relief. 

 These figures closely resemble the dust figures obtained by 

 Lichtenberg and Armstrong. ^ 



The character of the figures depend on 



(i) Whether the terminal over the dielectric is -1- or - . 



(2) The form and size of the -1- and - terminals. 



(3) The distance of the upper terminal from the surface of the 

 dielectric. 



(4) The character of the spark at the spark gap. 



(5) The density of the atmosphere. 



Permanent figures may be obtained by substituting ordinary 

 hard resin for the viscous mixture. The figures are then de- 

 veloped by warming and rendering the surface sufficiently plastic 

 to allow of movement. The persistence and fixity of the stresses 

 produced by a discharge on resin is remarkable, figures have 

 been developed two months after the discharge with very slight 

 diminution of effect. 



The density of the atmosphere exercises a great effect on the 

 figures obtained. As the density diminishes, the figures be- 

 come more diffuse and less marked in character, and at an air 

 pressure of 85 mm. a + figure becomes faintly marked by 

 bands without the characteristic rays. 



Geological Society, June 23.— Dr. Henry Hicks, F.R.S., 

 President, in the chair. —Notes on a collection of rocks and 

 fossils from Franz Josef Land, made by the Jackson-Harmsworth 

 Expedition during 1894-96, by E. T. Newton, F.R.S. , and J. 

 J. H. Teall, F.R.S. A large collection of rocks and fossils, 

 obtained by the members of the Jackson-Harmsworth Expedi- 

 tion, chiefly from the neighbourhood of Cape Flora, on the 

 south-west of Northbrook Island, but also from more distant 

 localities visited during boat- and sledge-journeys, have been 

 sent to the Director-General of the Geological Survey, and 

 examined by the authors. After a summary of what was 

 previously known of the geology of Franz Josef Land, an account 

 of the new specimens was given. The rocks are for the most part 

 basalts, and are described in detail ; they are usually formed of 

 labradorite, augite, and interstitial matter which is sometimes 

 represented by palagonite containing a large percentage of iron- 

 oxide. This palagonite is regarded as the hydrated representa- 

 tive of the residual magma left after the separation of labradorite 

 and augite ; and the conclusion is reached that in this case pro- 

 gressive crystallisation has resulted in the concentration of 

 iron-oxide in the mother liquor. Most of the fossils have been 

 collected around Cape Flora. The presence of Ammonites 

 viacrocephabis, A. viodiolaris, and Belemnites Panderi indicate 

 the presence of rocks of Lower Oxfordian or Callovian age ; 

 while, apparently above these, a plant-bed was met with in 

 which the genus Ginkgo is conspicuous, and this is believed to 

 be of Upper Jurassic age. The oldest fossiliferous bed yet 

 found occurs about twenty miles to the west of Cape Flora, and 

 also contains plant-remains, which, it is thought, may be Lower 

 Jurassic and possibly of the age of the Great Oolite. These plant- 

 beds and numerous indications of layers of lignite seem to show 

 that these Jurassic strata are to a great extent of esluarine or 

 fresh- water origin. The general structure of the country appears 

 to be typified by what occurs at Cape Flora, where cliffs of 

 sedimentary strata some 600 feet high (for the most part hidden 



1 "Electric Movements in Air and Water, with Theoretical Inferences.' 

 By Lord Armstrong, C.B., F.R.S. (London : Smith, Elder, and Co., 1897.) 



