498 



JVATt/RP. 



{April \%, 187-8 



GreifsWAld.— The University has received a grant of 

 381,000 marks for a new library building, and 200,000 marks 

 for the construction of a physical laboratory. 



SCIENTIFIC SERIALS 



Bulletin of the Nuttall Ornithohqical Club, A Quarterly 

 yournal of Ornithology. Vol. III. January, No. I. — This 

 journal, on entering upon its third volume, has increased its 

 quarterly numbers from a thin part of twenty-four pages to a part 

 containing forty-eight pages and a coloured plate. It will con- 

 tinue, as before, under the editorial management of Mr. J. 

 A. Allen, assisted by Prof. Baird and Dr. E. Coues, and it is 

 intended that the volume for the current year should contain an 

 exhaustive resu7ne of the current literature relating to North 

 American Ornithology. The present number contains — Dr. E. 

 Coues : On Passereulus bairdi (with plate), and P. princeps, — H. 

 W. Henshaw on the species of Passerella. — W. A. Cooper : On 

 the breeding of Carpodacus purpureus, var, Californicus. — W. 

 Brewster : On the first plumage of North American birds. — ^J. A. 

 Allen : On Wallace's theory of birds' nests. — N. S. Goss : Breed- 

 ing of the duck hawk in trees. — Notes of recent literature and 

 general notes. 



Keale Istituto Lombardo di Scienze e Letlere, Rendiconti, vol. xi. 

 f asc. iii. — On the action of so-called catalytic force viewed accord- 

 ing to the thermodynamic theory, by M. Tommasi.- — Study on the 

 dominant diseases of vines, by M, Garovalio and Cattaneo. — 

 On the chronology of Tyrrhenian volcanoes, and on the hydro- 

 graphy of the Val di Chiana previously to the niiocene epoch, 

 by M. Verri. — On the permanent magnetism of steel at different 

 temperatures, by M, Poloni. — On the plasmogonic production 

 of leptothrix and leptomitus, by M. Cattaneo. — On the refrige- 

 ration of pulverulent metallic solids (continued), by M. Cantoni. 



SOCIETIES AND ACADEMIES 

 London 



Royal Society, February 28.— " On the Reversal of the 

 Lines of Metallic Vapours," by G. D. Liveing, M.A., Professor 

 of Chemistry, and J. Dewar, M.A., F.R.S., Jacksonian Pro- 

 fessor, University of Cambridge. No. I. 



In order to examine the reversal of the spectra of metallic 

 vapours, the authors observe the absorptive effect produced on 

 the continuous spectrum emitted by the sides and end of the 

 tube in which the volatilisation takes place. For this purpose 

 they use iron tubes about half an inch in internal diameter, and 

 about twenty-seven inches long, closed at one end, thoroughly 

 cleaned inside, and coated on the outside with borax, or with a 

 mixture of plumbago and fireclay. These tubes are inserted in 

 a nearly vertical position in a furnace fed with Welsh coal, which 

 will heat about ten inches of the tube to about a welding heat, 

 and they observe through the upper open end of the tube, either 

 with or without, a cover of glass or mica. To exclude oxygen, 

 and avoid as much as possible variations of temperature, they 

 introduce hydrogen in a gentle stream through a narrow tube 

 into the upper part only of the iron tube, so that the hydrogen 

 floats on the surface of the metallic vapour without producing 

 convection currents in it. By varying the length of the small 

 tube conveying the hydrogen, they are able to determine the 

 height in the tube to which the metallic vapour reaches, and to 

 prevent further displacement of the vapour, and thus to maintain 

 different lengths of the iron tube full of metallic vapour at a 

 comparatively constant temperature for considerable periods of 

 time. 



By this means the following observations have been made up 

 to the present time : — 



The first metal experimented on was thallium, one of the most 

 volatile of metals. After arranging the current of hydrogen so 

 as to keep the tube free from air, but without any rapid move- 

 ment of the gas, they saw the characteristic line reversed, and 

 maintained it so for a considerable time. 



The metal indium, closely allied in its behaviour and volatility 

 to thallium, was next examined, and they observed the bright 

 blue line reversed. This was most plainly visible when that 

 portion of the vapour which was nearest to the sides of the tube 

 was looked through. 



They had great difficulty in preventing the oxidation of mag- 

 nesium in the tube, and in using tubes wider than half an inch, 



did not succeed in getting any reversal, but with half-inch tubes 

 the b lines were clearly and sharply reversed, also some dark 

 lines, not measured, seen in the blue. The sharpness of these 

 lines depended on the regulation of the hydrogen current, by 

 which the upper stratum of vapour was cooled. 



A piece of metallic lithium was introduced, and gave no re- 

 sults. Sodium was next added in the same tube, and this did 

 not bring out the reversal of the lithium lines. Similarly, chloride 

 of lithium and metallic sodium, introduced together, gave no 

 better results. To a tube containing potassium vapour, some 

 lithium chloride was added, but no lithium line appeared. On 

 adding metallic sodium to this -atmosphere, and more lithium 

 chloride, the bright-red lithium line appeared sharply reversed, 

 and remained well defined for a long time. It is worthy of 

 observation that the lithiuna line was only reversed in a mixture 

 of the vapours of potassium and sodium, and it seems highly 

 probable that a very slightly volatile vapour may be diffused in 

 an atmosphere of a more volatile metal, so as to secure a sufficient 

 depth of vapour to produce a sensible absorption. This would 

 be analogous to well-known actions which take place in the 

 attempt to separate organic bodies of very different boiling 

 points-by distillation, where a substance of high boiling-point is 

 always carried over, in considerable quantity, with the vapour of 

 a body boiling at a much lower temperature. It is a matter for 

 future investigation how far chemical interactions taking place in 

 a mixture of metallic vapours affect the volatility of a third body, 

 and what relation, if any, this may have to such phenomena as 

 the increased fusibility of mixtures of salts of potassium and 

 sodium, and the well-known fluidity of the alloy of those 

 metals. 



As the authors have had occasion to use sodium and potassium 

 in their tubes, they have had opportunities of observing the 

 absorption spectra of these metals, and they find that there is a 

 great deal yet to be observed in regard to these spectra. Up to 

 the present time they have not observed any of the appearances 

 noted by Lockyer, " On a New Class of Absorption Phenomena," 

 in the Proceedings of the Royal Society, vol. xxii., but they 

 have repeatedly noted the channelled-space spectrum of sodium 

 described by Roscoe and Schuster, in the s.ime volume of the 

 Proseedings. They observed in their tubes no channelled space 

 absorption by potassium, but continuous absorption in the red 

 and one narrow absorption band, with a wave-length of 5, 730, 

 not corresponding with any bright line of that metal. 



With reference to the absorption spectrum of sodium vapour 

 they remark that it is by no means so simple as has been gene- 

 rally represented. The fact that the vapour of soJium in aflame 

 shows only the reversal of the D lines, while the vapour, volati- 

 lised in tubes, shows a channelled space absorption, correspond- 

 ing to no known emission spectrum, appears to be part of a 

 gradational variation of the absorption spectrum, which may bs 

 induced with perfect regularity. Experiments with sodium, 

 carried out in the way described, exhibit the following succession 

 of appearances, as the amount of vapour is gradually diminished, 

 commencing from the appearance when the tube is full of the 

 vapour of sodium, part of it condensing in the cooler portion of 

 the tube, and some being carried out by the slow current of 

 hydrogen. During this stage, although the lower part of the 

 tube is at a white heat, we have always noticed, as long as the 

 cool current of hydrogen displaced metallic vapour, that, on 

 looking down the tube, it appeared perfectly dark. The first 

 appearance of luminosity is of a purple tint, and, with the spec- 

 troscope, appears as a faint blue band, commencing with a wave- 

 length of about 4,500, and fading away into the violet. Next 

 appears a narrow band in-the green, with a maximum of light, 

 with a wave-length of about 5,420, diminishing in brightness 

 so rapidly on either side as to appear like a bright line. This 

 green band gradually widens, and is then seen to be divided by 

 a dark band, with a wave-length of about 5,510. Red light 

 next appears, and between the red and green light is an enormous 

 extension of the D absorption lines, while a still broader dark 

 space intervenes between the green and the blue light. The 

 dark line in the green (wave-length about 5,510) now becomes 

 more sharply defined. This line appears to have been observed 

 by Roscoe and Schuster, and regarded by them as coinciding 

 Vi ith the double sodium line next in strength to the D lines, but 

 it is considerably more refrangible than that double line. In the 

 next stage, the channelled space spectrum comes out in the dark 

 space between the green and blue, and, finally, in the red. 

 Gradually the light extends, the channels disappear, the D lines 

 absorption narrows, but still the dark line in the green is plainly 



