Nov. 17, 1887] 



NATURE 



59 



which can be used as an end-on tube, and then, after getting 

 a vacuum so perfect that the spark will not pass, to slightly heat 

 the metal. After a time the spectrum of hydrogen, sometimes 

 accompanied by the low-temperature flutings of carbon, begins to 

 be visible alike from the sodium and the magnesium. 



If the vacuum has been very perfect to start with, the bright 

 lines C and F will at first be visible without any trace of structure, 

 and the hydrogen will be of a magnificent red colour. If now 

 the actio:! of the pump be stopped and the sodium be still more 

 heated, a p^int will be reached at which the conductibility of the 

 gas is at its maximum, and then, the jar not being in circuit, the 

 structure-spectrum of the gas will be seen absolutely alone, 

 without any trace of either C or F. The gradual disappearance 

 of the F line is very striking, and when the bright line is out of 

 the field the lines due to the structure seem to be enhanced in 

 brilliancy. 



The brightest part of the spectrum is then that near D ; in the 

 blue-green we have a line at 464 more refrangible than F, 

 iind then a doube line at 4930 and 4935 ; other less re- 

 frangible lines are seen. These are phenomena seen associated 

 with sodium, but if we use the hydrogen produced from a piece 

 of magnesium wire or from a crystal of olivine, under the same 

 •circumstances we find that so far a? the lines of hydrogen go 

 the phenomenon remains the same, but that there is then visible 

 in the spectrum a line at 500, which has been recorded in the 

 spectrum of magnesium under other conditions, not only by 

 myself but by Dr. Copeland.^ 



F. Experiments upon the spectra of meteorites at low 

 ■temperatures. 



All the later observations recorded have been made on 

 tmdoubted meteorites, fragments of whic'.i have been in the 

 kindest manner placed at my disposal. 



I. In the oxyhydrogen flame. 

 The observations gave in all only about ten or a dozen lines 

 belonging to the metals magnesium, iron, sodium, lithium, 

 an 1 potassium, and two flitings, one of manganese, and one of 

 iron. 



II. With a quantity coil without jar. 



The observations gave in all abaut twenty lines belonging to 

 the metals magnesium, sodium, iron, strontium, barium, calcium, 

 chromium, zinc, bismuth, and nickel, and four lines of unknown 

 origin. 



III. When heated in a vacuum tube when a cuiTent is 



passing along it. 



A small piece of iron meteorite was inclosed in the middle of 

 a horizontal tube, so that the spark might be made to pass 

 through the tube and over the meteorite. After complete ex- 

 haustion has been obtained, the first spectrum observed when 

 the tube, end on, is placed in front of the spectroscope, is a 

 spectrum of hydrogen. The carbon flutings are only visible 

 occasionally. If the meteorite then be very gently warmed by 

 placing a Bunsen burner at some distance below the tube, the 

 glow over the meteorite is seen to change its colour, and the 

 line at 500 is constantly, and another line at 495, apparently 

 exactly in the position of the second line of the spectrum of 

 the nebula:, is occasionally, seen. This line is more refrangible 

 than th; structure line of hydrogen in this region, which occupies 

 the same position as the barium line. This, however, if the 

 heating is continued, especially in the case of stony meteorites, 

 is soon succeeded by a much more brilliant green glow, in 

 ■which magnesium b and many other lines appear, now accom- 

 panied by the carbon flutings. The observations made under 

 all the above conditions are shown in Maps 2 and 2A. 



In these observations if a line in the meteorite spectrum were 

 coincident with a metallic line, with the dispersion employed, in 

 the absence of the brightest line of that metal, the line was re- 

 garded as originating from some other substance. Thus a line 

 was sometimes seen at 5480, apparently coincident, with the dis- 

 persion employed, with the green lines of Sr and Ni ; sometimes 

 the brightest line of Sr at 4607 was absent, and it was then fair 

 to assume that the presence of 5480 was due to Ni, but in the 

 presence of 4607 it might be due to Sr. 



!' ^"° ''^'^ table must be added 500 '6 mmm. as the wave length of tlie first 

 line in the great band of magnesium as determined by M. Lecoq de Bois- 

 biudran from the spark-spectrum of the chloride of that metal, which 

 evidently agrees with the flame-spectrum, in this region at least. It is 

 worthy of mte that this line almost abio'utely coincides with the brightest 

 hne in the spectra of planetary nebulx " (D.-. Copeland, Copernicus, vol. ii. 

 p. 109). 



COMPARISOMS OF THE FOREGOING OBSERVATIONS AMONG 



themselves and with those made on various orders of 

 \ Celestial Bodies. 



Tha discussions have taken, in the first instance, the form 

 of comparisons of the different phenomena observed, and for this 

 purpose all recorded observations of flutings and bright lines 

 and dark lines in stars, comets, nebula;, &c., have been carefully 

 mapped in addition, all records having, when necessary, been 

 brought to a common scale. Having these maps, I could then 

 compare the totality of celestial observations with the laboratory 

 work to which reference has already been made. 



The following are among the comparisons already dealt 

 with : — 



I. The spectra of meteorites observed under the various 

 conditions, chiefly considering magnesium, iron, 

 and manganese, with the bright lines observed at 

 low temperatures. 



The main conclusions are : — 



(i) That only the lowest temperature lines of Mg, Na, Fe, Cr, 

 Mn, Sr, Ca, Ba, K, Zn, Bi, and Ni are seen in the meteorites 

 under the various conditions. They are not all seen in one 

 meteorite or under one particular condition ; the details of 

 individual observations are fully recorded in Maps 2 and 2A. 



(2) That in the case of Mg the line most frequently seen 

 is the remnant of the fluting at 500, while in a photograph 

 the main ultra-violet line recorded is the one at 373, previously 

 recorded under these conditions by Messrs. Liveing and Dewar. 

 In the quantity spark other lines are seen, notably b-^, /'._„ b^, 

 and 5201. The line at 500 was considerably brightened when the 

 number of cell; was reduced, thus showing it to be due to some 

 molecule which can exist best at a low temperature. 



(3) That in the case of Mn the only line visible at the tempera- 

 ture of the bunsen burner, 5395, is the only line seen in the 

 meteorites. 



(4) That the lines of iron seen in the meteorites are those which 

 are brightest when wire gauze is burned in the flame. The chief 

 of these are 5268, 4383, 5790, and 6024 ; it is possible, however, 

 that the two latter are due to some substance, not iron, cojimon 

 to the gauze and the meteorites. 



II. The spectra of meteorites generally, with the bright 

 lines and flutings seen in luminous meteors, 

 comets, and some "stars." 



a. Luminous meteors. 



With regard to the records of luminous meteors, it may be 

 remarked that the observations, so far as they have gone, have 

 given decided indications of magdesium, sodium, lithium, potas- 

 sium, and of the carbon flutings seen in comets. The following 

 quotations from Konkoly and Prof. Herschel are among the 

 authorities which may be cited for the above statement. 



"On August 12, 13, and 14, I observed a number of meteors 

 with the spectroscope ; amongst others, on the 12th, a yellow 

 fireball with a fine train, which came directly from the Perseid 

 radiant. In the head of this meteor the lines of lithium were 

 clearly seen by the side of the sodium line. On August 13, at 

 loh. 46m. los. , I observed in the north-east a magnificent fire- 

 ball of emerald-green colour, as bright as Jupiter, with a ver>- 

 slow motion. The nucleus at the first moment only showed a very 

 bright continuous spectrum with the sodium line ; but a second 

 after I perceived the magnesium line, and I think I am not 

 mistaken in saying those of copper also. Besides that, the 

 spectrum showed two very faint red lines." ^ 



"A few of the green 'Leonid' streaks were noticed in 

 November (1866) to be, to all appearances, monochromatic, or 

 quite undispersed by vision through the refracting prisms ; from 

 which we may at least very probably infer (by later discoveries 

 with the meteor-spectroscope) that the prominent green line of 

 magnesium forms the principal constituent element of their 

 greenish light." ^ 



Again, later on in the same letter, Prof. Herschel mentions 

 Konkoly's observation of the bright b line of magnesium in 

 addition to the yellow sodium line in a meteor on July 26, 1873. 



I again quote from Prof. Herschel : — 



" On the morning of October 13 in the same year, Herr von 

 Konkoly again observed with Browning's meteor spectroscope 

 the long-enduring streak of a large fireball, which was visible t« 



' Konkoly, Observatory, vol. iii. p. 157. 



^ Herschel, letter to Naturb, vol xtiv. p. 507. 



