170 



NATURE 



[Dec. 1 8, 1879 



direction of the currents was the most uniform. This is in 

 accordance with the common truth in science, that the smallest 

 phenomena are the most constant. 



The author has ascertained by separate experiments of a dif- 

 ferent kind that mercury, when sufficiently agitated with solu- 

 tions neutral to test paper, of salts of the alkali metals, renders 

 some of those liquids feebly alkaline ; the effect, however, is so 

 slight, requires such extensive and long-continued contact of the 

 substances that it appears consistent with the view that chemical 

 action is not the cause of the currents in these thermo-electric 

 experiments. 



" Quantitative Spectroscopic Experiments," by Prof. G. D. 

 Liveing, M.A., F.R.S., and Prof. James Dewar, M.A., F.R.S. 



"On the Spectra of Sodium and Potassium." By G. D. 

 Liveing, M.A., F.R.S. , Professor of Chemistry, and J. Dewar, 

 M.A., F.R.S., Jacksonian Professor, University of Cambridge. 



The authors notice that as seen in the electric arc in one of 

 their lime crucibles, there are in each spectrum several lines 

 hitherto undescribed, which make the whole very regular and 



symmetrical. The authors have generally used carbonates of 

 the metals, sometimes chlorides. 



The pair of lines (5155, 5152) are sharply defined, and have 

 no other line close to them ; but the bright green pair, or fifth. 

 group (4983, 4982), are diffuse lines, usually seen as one band, 

 but noted by Lockyer to be a double line, and have a third line 

 on their more refrangible side. The authors feel sure that there 

 ought to be a fourth line in this group, but have never been able 

 to detect it. 



The sixth group consists of a pair of lines sharply defined. 

 The first only of this pair is described by Lecoq de Boisbaudran. 

 The seventh group is a pair of lines with diffuse edges, which 

 the authors have seen reversed as fine dark lines in the middle of 

 diffuse blue bands. The first only is described by Lecoq de 

 Boisbaudran. By putting some titanic oxide into the crucible 

 the titanium line 4666*5 was seen between the sodium lines, and 

 the authors have no doubt that it is sodium which gives the 

 winged appearance to the corresponding ray in the solar spectrum. 

 The eighth group is a more sharply defined pair, the ninth a 

 diffuse pair, the tenth gr oup again a more sharply defined pair, 



Dia, / Spectrum, of sodium, x/v b\e arc 



-"■'I',. ::':'! inriiiiMUiifliiitiiuii^jiTT 



48 47 46 45 44 



lll!"lllllhllllllllllllllllll|llilllill|ll!l:mi! 

 6200 6) 60 53 58 



.ii|i!iiiiiii|iiiiiniiiiii:ii; 



5/ 56 55 5* J3 



5S 5) 



<5 



and the eleventh group a very diffuse pair, sometimes seen as a 

 continuous band dividing as the sodium evaporates. The twelfth 

 group is a diffuse but narrow band, which the authors have not 

 seen divided, and the thirteenth group a diffuse broad band 

 nearly bisected by the iron line 4325. 



The successive groups become fainter and more diffuse as 

 they are more refrangible, at the same time the distance between 

 successive groups diminishes. Their positions are shown on the 

 accompanying diagram to a scale of wave-lengths. It is worthy 

 of note that every alternate group is much more sharply defined 

 than the others. Moreover, it is only the diffuse groups (3) (5) 

 (7) which show reversal except the first group, in the orange, 

 which, however, is more difficult of reversal than the others. 

 The whole series, exclusive of D, looks very like repetitions of 

 the same set of vibrations in a harmonic progression ; the first 

 (visible) term consisting of the six vibrations represented by the 

 orange pair (6160, 6154) and the four lines of group (3) ; the 

 next term of the five lines of the fourth and fifth groups, one of 

 the six vibrations being now too faint to be seen ; the next three 



terms, of each of which only four lines are visible, consisting of 

 the six and seventh, the eighth and ninth, and the tenth and 

 eleventh groups, and the last term of the two faint bands of the 

 twelfth and thirteenth groups. 



Simple harmonic relations can be found to subsist between 

 some of the groups, for instance, the wave-lengths of the. fifth, 

 seventh, and eleventh groups are very nearly as ^ : T '„ : T V, but 

 the whole series cannot be represented as simple harmonics of one 

 set of six vibrations with any probability. The smallest numbers, 

 which are nearly proportional to the reciprocals of the wave- 

 lengths of groups (1), (4), (6), (8), (10), (12), are 81, 97, 105, lie, 

 113, 115 ; and these numbers are only approximately in the same 

 ratios as the reciprocals of wave-lengths. 



Lines closely corresponding to all these lines except the faint 

 ones of the 3rd and 5th groups, and the last two groups are 

 found in the solar spectrum. 



The potassium spectrum as seen in the arc, leaving out of 

 account the two pairs of lines in the red and that in the violet, 

 consists of a series of groups of four lines each, succeeding one 



J)ul 2. jSpeclrum, of potassium, between- D & G 

 J) 



|i i iii mii iiii H i ™ i ini i n i ii ii iii i i iiiiii[ | iii i iii i i | i ii i i i i i im 



6X0 60 59 58 57 56 55 54 53 52 51 50 49 48 47 46 45 44 <U 



another at shorter intervals and becoming fainter as they are more 

 refrangible. They all are more or less diffuse, markedly more 

 so on their less refrangible edges. They are shown on the 

 accompanying diagram to a scale of wave-lengths. 



The first and least refrangible group of this series consists of 

 the four lines to which Lecoq de Boisbaudran assigns the wave- 

 lengths 5831, 5812, 5S01, 5783. The second of these lines 

 (5812) is much less strong than the others as seen in the spark. 

 In the arc they are all nearly equal in brightness, but the authors 

 have not seen the second line reversed. Six groups of four lines 

 each follow. 



The sixth group has lines of about the wave-lengths 4808, 4803, 

 4796, 4788. 



The seventh group is too faint and diffuse to be distinctly 

 resolved. The wave-length of the least refrangible edge is about 

 4759- 



None of the last three groups are seen by Lecoq de Bois- 

 baudran, and they are too diffuse for exact measurement ; on the 

 other hand, he gives several other lines which are not noticed in 

 the arc. 



As in the case of sodium the repetition of these quartets of 

 lines at decreasing intervals with decreasing brightness and sharp- 

 ness as they proceed from the less to the more refrangible, gives 

 the impression of a series of harmonics ; but the wave-lengths do 

 not seem to be in a simple harmonic progression, though simple 

 harmonic relations may be found between some of the groups. 



Linnean Society, December 4. — Prof. Allman, president, 

 in the chair. — Mr. W. Carruthers exhibited a bottle of Pteropods 

 {Spinalis retroveruts) obtained in abundance by Dr. J. Grieve in 

 the Gareloch, Ross-shire, Scotland, in July. A letter trom Dr. 

 Grieve was read, wherein he states that these mollusca swam 

 rapidly to the surface, rising with a perpendicular fluttering 

 motion, and having reached the top they raised their wing-like 

 appendages above their heads, and thus upholding them motion- 

 less, would then drop quietly to the bottom. Some of the 

 pteropods would occasionally stop half way, and paddle back to 

 the surface to repeat the falling motion ; seldom or ever did they 

 swim along the surface. Dr. Grieve did not witness the creatures 

 use their wings (epipodia) as feet to walk or crawl along the 



