114 



NATURE 



[May 30, 189! 



instrumental values of the latitude. Circumstances prevented 

 him from carrying on the work until six years later, when he took 

 up the problem again. The results then obtained are published 

 in a series of eighteen papers in the .■tslroiwiiiita/ Journal {l$<)\- 

 94), exclusive of a series of five papers upon a topic clo.sely 

 related thereto, namely, the aberration-constant. These papers 

 have been noted from time to time in this column, so it is 

 unnecessary to do more than refer to them now. 



In connection with variable stars, liesides the incidental work 

 of observation and discovery which Dr. Chandler has contribute<l 

 to it, his work has involved the collection of all the data in 

 astronomical history, their discussion, and the formulation of 

 the elements of their light-variations into numerical laws. Hi^ 

 important researches upon cometary orbits are also well known 

 to astronomers. 



A LECTL'RE EXPERIMENT. 

 A hL'KTHER description of the use of the electric furnace 

 ■^^ recently exhibited at the Royal Society, for the purpose of 

 lecture demonstrations, may be useful, as pictures, some six feet 

 across, of the interior of the furnace may readily be projected on 

 the screen. This is effected by the aid of the device which 

 has already been given in Nature (p. 17, Fig. 2). The result 

 is really very l«autiful, though it can only l>e rendered in dull 

 tones by the accompanying illustration (Figs. .\, B). It may be 

 well, therefore, to state briefly what is seen when the furnaci- 

 is arranged for the melting of metallic chromium. Directly 

 the current is passed, the picture reflected by the mirror, F. 

 (Fig. 2, loc. <//.), shows the interior of the furnace (fig. A)like a 

 dark crater, the dull red poles revealing the metallic lustre 

 and grey shadows of the metal beneath them. .-^ little 

 later these poles Viccome tipped with dazzling white, and, 

 in the course of a few minutes, the temperature rises to 

 about 2500' C. Such a temperature will keep chromium well 

 melted, though a thousand degrees more may readily he attained 

 in a furnace of this kind. V.:\ch i»'le is >-"-n =urrniinfkrl wilh a 



the little crater ; while if the current is broken, and the light dies 

 out, you wish that Turner h.i<l paintedthe limpid tints, and that 

 Kuskin might describe their loveliness. 



The effect when either tungsten or silver replaces chromiimi is 

 much the same, but, in the latter case, the glowing lake is more 

 brilliant in its turbulent lx)iling, and blue vapours rise 10 he 

 condensed in iridescent beads of distilled silver which stud the 

 crater walls. 



Fic. A.— Thi* rrpr«cnt« Ihc interior of the furnace conlainine mollen 

 chrGiniufn a\ i% seen cither by reflection on .1 screen or by lookine into 

 ihc furn.icc from above, the eye^ being suitably protected by deeply 

 limed ^la^M^«. 



lamlicnt halo of the green-blue hue of the sunset, the central 

 Ijciml »>f the arc changing rapidly from peach-blossom to 

 Livendcr and purple. The arc can then l<c lcnglhene<l, and as 

 '* • ' 1 further and further .asunder, the irregular 



" ■ ' fuse in silver droplets, below an intense blue 



fi' ' "''" green of lustrous emerald ; then the 



'■1 m melt into a .shining lake, which re- 



"" 11 a glory of green and gold shot with 



orange )„n.-. .Mill a lew minutes later, as the chromium bums, 

 a shower irf brilliant sparks of metal arc projected from the 

 furnace, amid the clouds of russet or brown vapours which wreath 



NO. 1335, VOL. 52] 



Fig. b. — In this case ihcarc was broken the instant before the phologr.iph \va 

 taken. The furnace contained a bath of silver just al its boilint; point. 

 The reflection of the poles in the bath, the globules of distilled silvci , 

 and t.ie drifting cloud of silver vapour, are well shown. 



Such experiments will probably lend a new interest to the us ■ 

 of the arc in connection with astronomical metallurgy, for, a,* 

 George Herbert said long ago — 



" Stars have their stormit even in a high degree, . 

 .\s well as we " ; 



and Lockyer has shown how important it is, in relation to such 

 storms, to be able to study the disturbances in the various strata 

 t)f the stellar or solar atmosphere. Layers of metallic va|xiur 

 which differ widely in temperature can be more readily obtaineil 

 by the use of the electrical furnace than when a, fragment of 

 metal is melted and volatilised by placing it in the arc, in a 

 cavity of the lower carbon. W. C. Roberts-Austen. 



THE LIFE-HISTORV OF THE CRUSTACEA 



LV EARLY PAL.EOZOIC TIMES. 

 T X his recent anniversary address to the CJeological Society, 

 '■ the I'resident, Dr. Henry Woodward, K.K.S., after 

 the usual distribution of medals and awards, the reading 

 of oliituaries of deceased Fellows, and some preliminary 

 matters relating to the affairs of the Society, incluiling the moot 

 <|uestion of the introduciiim of ladies as visitors Iti the evening 

 meetings, devoted the remainder of his address to a brief dis- 

 cussion of " Some I'oints in the Life-hislory of the Crustacea 

 in Early Paleozoic Times." Dr. Woodward continued as 

 follows: — "Of the various groups of the Invertebrata whose 

 ancestry extends into I'al.xozoic limes, none possess a greiiter 

 interest for the geologist than the Crustacea, whose existence is 

 proved as far back as the Lower Cambrian rocks ; while their 

 near allies, the Arachnida, have been met with in str.-ila as old 

 as the Silurian. 



" My earliest papers on the Eurypterida appeared in 1863 and 

 1864, and an account of .S/)'/(JH//r/M and //<•«; /«.i/>(j was com- 

 municated to this .Society in 1865, just thirty years ago. In that 

 year ( 1865) I h.id the pleasure, with my friend and fellow-worker, 

 the late J. W. Salter, K.ti.S., of publishing a • Chart of Fossii 

 Crustacea,' in which an attempt was made to show the evolution 

 in time of the various forms belonging to this class, graphically 

 depicted on an engraved folding-sheet, with explaivilory text. 

 In it we ]K)inted out that the main development of the Crustacea 

 in I'aheozoic times consisted of the gre.it groups of the Trilobita, 

 the Kur)pteiida, the Ni|ihosura, the l'hyllo|Mida, and the 



