214 



NA TV RE 



\_June 29, 1882 



attainable is doubtless far below that of the arc, but still it is 

 quite sufficient to maintain iron and aluminium in the state of 

 vapour, and show the reversal of the lines of these elements 

 with singular sharpness. The temperature of the interior is 

 sufficienti'v high to transform the diamond into coke, even in a 

 current of hydrogen, and the result may be taken as proving 

 that the temperature is above that of the oxyhydrogen flame. 



The apparatus is thus constructed : — A rod of carbon, 15 

 millims. in diameter, perforated down its axis with a cylindrical 

 hole 4 millims. in diameter, is passed through a hole in a lime 

 block, and is connected with the positive electrode of a Siemens' 

 dynamo electric machine ; another carbon rod, unperforated, is 

 passed into the lime block through a second hole at right angles 

 to the first, so that its end meets the middle of the other rod 

 inside the block of lime. The second rod is connected with the 

 negative electrode of the dynamo-machine, and after contact is 

 made between the two rods, is raised a little, so that the arc 

 discharge continues between the two carbon rods within the 

 block of lime. In this way, the outside of the perforated rod 

 or tube becomes intensely heated, the heat is retained by the 

 jacket of lime, and the interior of the tube gradually rises in 

 lemperature, and attains in the central part a very high point. 

 By stopping the arc it can be made to pass through the same 

 Mages of temperature in the inverse order. Observations are 

 made by looking down the perforation. When the light issuing 

 from the tube is projected by a lens on to the slit of a spectro- 

 scope, the heated walls of the tube give at top and bottom a 

 continuous spectrum, against which various metallic lines are seen 

 reversed, while in the central part, when the tube is open at the 

 farther end, the spectrum is discontinuous, and the metallic lines 

 seen reversed against the walls at top and bottom, appear as 

 bright lines. 



By passing a small rod of carbon into the perforation from 

 the further end, a luminous background can be obtained all 

 across the field, and then, as the walls of the tube are hotter than 

 the metallic vapours between them and the eye, the metallic 

 lines are only seen reversed. A very slight alteration in the 

 position of the carbon rod makes the lines disappear, or re- 

 appear, or show reversal, and as the core is adjusted by eye- 

 observation before photographs are taken, all the conditions of 

 the experiments ars thoroughly known and are under easy control. 

 The authors have taken photographs of the violet and lower part 

 of the ultra-violet spectrum given by the tube at successive inter- 

 vals while the temperature was rising, and noted the following 

 results. When commercial carbons were used the first lines to 

 be seen as the temperature rose were the potassium lines, wave- 

 length 4044-6, next the two aluminium lines between H and K 

 became conspicuous, then the manganese triplet about wave- 

 length 4034, and the calcium line, wave-length 4226, then the 

 calcium lines near M and an iron line, probably M, between 

 them, and then gradually a multitude of lines which seem to be 

 all the conspicuous iron lines between O and h. At this stage, 

 when the small rod is used to give a background, the bright 

 continuous spectrum is crossed by a multitude of sharp dark 

 lines, vividly recalling the general appearance of the solar spec- 

 trum. In the higher region the continuous spectrum extends 

 i.eyondthe solar spectrum, and the magnesium line, wave-length 

 2852, is a diffuse dark band, while all the strong iron lines about 

 T, and the aluminium pair near S, are seen as dark lines. The 

 behaviour of the calcium lines H and K is peculiar. These lines 

 are often absent altogether, when the line wave-length 4226 and 

 the two near M are well seen, and when the two aluminium lines 

 between them and many of the iron lines are sharply reversed. 

 Even the introduction of a small quantity of metallic calcinm or 

 calcium chloride into the tube did not bring them out reversed. 

 They were only seen as bright lines, not very strong, when the 

 small rod was removed. 



In some of the photographs H is visible as a bright line with- 

 out K. The authors have formerly observed that K shows 

 reversal in the electric arc spectrum taken in a lime crucible on 

 the addition of aluminium, when H remains bright, and such a 

 condition as that shown by the hollow carbon tube when H is 

 present without K, might legitimately have been predicted. The 

 lithium lines at 4603 and 4131 are often bright when many other 

 lines in the neighbourhood are reversed, and must therefore be 

 regarded as relatively difficult of reversal. As a rule, the lines 

 less refrangible than 4226 are balanced as to their emissive and 

 absorptive power and therefore disappear, while the more 

 refrangible are reversed. The cyanogen group at 3883 remain 

 bright when the iron lines on either side are reversed ; they often, 



however, disappear on the continuous spectrum. Many lines 

 about F end Q of the solar spectrum are reversed. The cyanogen 

 band above K is generally to be found in the photograph- of 

 the spectrum when only air is in the tube. It is then very faint, 

 and is the only cyanogen group visible. If ammonia is passed 

 into the tube the fine set above K, the N group, and, although 

 less plainly marked, the set at 4218 appear. In one plate the 

 thin lines at 43S0 and the group of seven at 4600 appear along 

 with the blue hydrocarbon set. It is well known that ammonia 

 reacts on carboh at a white heat, producing cyanide of am- 

 monium and hydrogen, so that the genesis of the cyanogen 

 spectrum under the present conditions is a crucial test of the 

 validity of the author's former observations on this subject. 



Both the indium lines 4101 and 4509 are persistently reversed, 

 together with several lead lines. Tin gives lines partly reversed 

 in highly refrangible portions of the spectrum, and silver gives a 

 fine fiuted-looking spectrum in the blue. Chloride of calcium 

 gives a striking set of six or seven bands about M, which may 

 be seen both bright and reversed. 



When the small rod is removed, it is easy at any moment to 

 sweep out the vapours in the tube by blowing through it ; it 

 is equally easy to pass in reducing or other gases. Ammonia 

 introduced seems to facilitate the appearance of reversed line*. 

 On passing this gas through a tube containing magnesia, the 

 set of lines just below b, which the authors have always found 

 to be associated with the presence of magnesium and hydrogen, 

 and is most probably due to some compound, instantly appear. 

 When the authors can command several electric arcs to heat a 

 considerable length of carbon tube, and are enabled to examine 

 the radiation of a powerful arc passing through the vapour in the 

 tube, valuable result* may be anticipated. 



Linnean Society, June 15. — Sir J. Lubbock, Bart., M.P., 

 F.R.S., in the chair. — The following gentlemen were elected 

 Fellows of the Society : — The Rev. R. Collie, Chas. A. Ferrier, 

 1. D. Gibson-Carmichael, Sir J. R. Gibson-Maitland, Bart., W. 

 D. Gooch, M. Murphy, Rev. H. A. Soames, II. C. Stephens, 

 H. G. W. Stephens, and James Turner. — Mr. W. T. Thiselton 

 Dyer exhibited specimens of Equis'tum gigatittum from Brazil, 

 which is said to have aerial stems attaining 30 feet. — Mr. C. B. 

 Clarke drew attention to a bundle of Hampshire Orchis, in 

 support of his view regarding the O. incarnata, L. — Mr. H. N. 

 Ridley showed a Carex glauca with two pediceled spikes and 

 lower male spike, each arising from a complex utricle ; and he 

 also showed a specimen of Lolium fersnne exemplifying transi- 

 tion from plumes to carpellary leaves. — Mr. G. J. Fookes ex- 

 hibited and explained peculiarities of malformation in specimens 

 of wallflower and Clematis lanuginosa, var. alba. — Sir John Kirk 

 gave information concerning specimens of fruit leaves and the 

 rubber of Landolphia florida obtained from the island of Pemba, 

 North Zanzibar ; and he showed native bells and rubber beaters 

 from East Central Africa, pointing out the beaters were the only 

 application of the rubber made use of by the negroes. — Sir J. D. 

 Hooker read a paper on " Dyera," a new genus of rubber-pro- 

 ducing plants belonging to the natural order Apocyneae, from 

 the Malayan Archipelago. The nearest affinity is with Alstonia, 

 from which it differs in the sessile stigmas and singular pistils. 

 Its flower is very minute, scarcely i-Sth of an inch long, and 

 ovules of I-200th of an inch diameter, yet these are succeeded 

 by fruits of immense size. — The next communication was on the 

 caoutchouc-yielding Apocynacen; of Malaya and Tropical Africa, 

 by W. T. Thiselton Dyer (for which see science notes). — 

 Prof. E. Ray Lankester afterwards read notes on some 

 habits of Scorpions. Of Androclonus funestris, Ehr., he 

 referred to their manner of burrowing in the sand, making 

 horizontal tunnels occasionally 8 inches long. The process 

 of exuviation was described, the scorpion then pushing its 

 large chela; into the sand and scraping rapidly backwards 

 with the three anterior pairs of walking legs. Androctonus in 

 walking raises its body well from the ground, and carries the 

 tail and sting arched over the back, thus differing from Ens- 

 corpius, which keeps the body low, and drags the tail behind, 

 with only the very tip bent. Androctonus feeds at dusk, seizing 

 its prey with the left chela, and, swinging fiie tail overhead, 

 pierces its victim, and, afterwards grasping the body by the 

 short chelicera?, sucks the nutrient substances. The comb 

 ordinarily is not sensitive, though it may be more so during the 

 breeding season. Specimens of Euscorpius fought with each 

 other, then using the chelae, and not the sting. — Mr. G. Brook 

 read a paper on a new genus of Collembola (Sinel/a), allied to 



