56 



NATURE 



{Nov. 17, 1887 



swarms of meteorites moving around a bright or dark body, the 

 maximum light occurring at periastron. 



XIII. The spectrum of hydrogen seen in the case of the 

 nebulte seems to be due to low electrical excitation, as happens 

 with the spectrum of carbon in the case of comets. Sudden 

 changes from one spectrum to the other are seen in the glow of 

 meteorites in vacuum tubes when a current is passing, and the 

 change from H to C can always be brought about by increased 

 heating of the meteorite. 



XIV. Meteorites are formed by the condensation of vapours 

 thrown off by collisions. The small particles increase by fusion 

 brought about again by collisions, and this increase may go on 

 until the meteorites may be large enough to be smashed by col- 

 lisions, when the heat of impact is not sufficient to produce 

 volatilization of the whole mass. 



XV. Beginning with meteorites of average composition, the 

 extreme forms, iron and stony, would in time be produced as a 

 result of collisions. 



XVI. In recorded time there has been no such thing as a 

 "world on fire " or the collision of masses of matter as large as the 

 earth, to say nothing of masses of matter as large as the sun; 

 but the known distribution of meteorites throughout space indi- 

 cates that such collisions may form an integral part of the economy 

 of Nature. The number of bodies, however, subject to such 

 collision is small, and must, it would appear, form but a small 

 percentage of the celestial bodies, seeing that they must be 

 consolidated. 



XVII. Special solar applications. 



a. The solar spectrum can be very fairly reproduced (in some 

 parts of the spectrum almost line for line) by taking a composite 

 photograph of the arc spectrum of several stony meteorites, 

 chosen at random, between iron meteoric poles. 



/3. The carbon which originally formed part of the swarm 

 the condensation of which produced the sun has been dissociated 

 by the high temperature brought about by that condensation. 



y. The indications of carbon which I discovered in 1874 

 (Proc. R. S., vol. xxvii. p. 308) will go on increasing in intensity 

 slowly until a stage is reached when, owing to the reduction of 

 temperature of the most effective absorbing layer, the chief 

 absorption will be that of carbon — a stage in which we now find 

 the stars of Class Ill.i^ of Vogel's classification. 



5. At the present time it seems probable that among the chief 

 changes going on in the solar spectrum are the widening of K 

 and the thinning of the hydrogen lines. 



Experiments upon which the Foregoing Conclusions 



DEPEND. 



A. Experiments upon carbon. 



The main conclusions which may be stated here are that there 

 are two systems of flutings which depend upon temperature 

 only. 



At low temperatures all compounds of carbon give a set of 

 simple flutings, the brightest of which are at wave-lengths 4510, 

 4830, 5185, and 5610. At higher temperatures there is a series 

 of. compound flutings, the brightest edges of which are at wave- 

 lengths 4380, 4738, 5165, and 5640. In the case of compounds 

 of carbon with hydrogen there is an additional fluting at wave- 

 length 4310, and this is the only criterion for the presence of 

 hydrocarbon among the flutings shown on thei map. (See 

 Map 3.) 



B. Experiments upon the luminous phenomena of the various 

 metals volatilized in the bunsen burner and the oxy-coal-gas 

 blow-pipe flame as compared with the phenomena seen at higher 

 temperatures. 



The main conclusions are that certain lines, bands, and flutings 

 are seen in the bunsen burner, that a larger tiumber is seen in 

 the flame, and that the total number seen in the burner and 

 flame is small. 



The order of visibility in the bunsen is, roughly — 



Mg 



Na 



Li 



Tl 



Sr 



Ba 



Ca 



K 



Mn 



Bi 



Lines 



Ca 



Bands \ Sr 



Ba 



Flutings {^^ 



All the observations both of bunsen and oxyhydrogen flame 

 may be condensed as follows : — 



In metals of the alkalies 



,, ,, alkaline earths 



In magnesian metals .. 

 In iron metals ... 



In metals which yield acids ... 



In copper metals 

 In noble metals 

 In earthy metals 



Na 

 K 

 Li 

 Ca 

 Sr 

 Ba 

 Mg 

 Zn 

 Cd 

 Fe 

 Ni 

 Co 

 Mn 

 Cr 

 Bi 

 Ti 

 W 

 Cu 

 Tl 

 Ag 

 Hg 

 Ce 



The following table shows the positions of the principal lines, 

 bands, and flutings seen in the spectrum of each of the metals 

 examined, arranged roughly in the order of their intensities. 



It should here be stated that as some of the researches have 

 had to deal with feeble illumination small dispersion has been 

 of necessity employed, and to make the observations along the 

 several lines comparable a one-prism spectroscope has been so 

 far used throughout. Hence the wave-lengths given are in all 

 cases only approximate. With this proviso the lines observed 

 have been as follows :— 



/« hunsen- 

 Mg 

 Na 

 Li 

 Tl 



Sr ^ 

 Ba 

 Ca 

 Mn 

 K 

 Bi 



5183 

 5889 

 6705 



5349 

 4607 



5534 

 4226 



5395 

 6950, 



4722 



5172, 5167, 4586, 5201. 

 5895- 



J • . /Seen on passing from the temperature of the 

 bunsen to that of the oxy-coal-gas flame — 



Fe 5268, 5327, 5371, 4383, 5790, 6024. 



Cu 5105, 5781, 5700. 



Cr 5202, 5203, 5207, 5410. 



Zn 4810, 491 1. 



Cd 5085. 



Ni 5476. 



Tl 5128, 5338. 



w 5490, 551 1- 



• Ag 5208, 5464. 

 Hg 5460. 

 Ce 5273, 5160. 



In bunsen — 



Ca 5535, 6250, 6500, 6000. 



Sr 6050. 



Ba 5150, 5250, 5330, 4860. 



\Seen on passing from the temperature of the 

 I bunsen to that of the oxy-coal-gas flame — 

 I Co 4710, 4920, 5170, 5460. 



Bands 



