90 



NA TURE 



\ytme A,, 1874 



gen gas rendered incandescent, you would see a line of a 

 certain thickness, with a certain pressure. Looking through 

 thesun's coronal atmosphere in an eclipse, you pierce seven oreight 

 hundred thousand miles oi'hydrogen gas. Thethicknessof the lines 

 is the same. Various thicknesses of sodium vapour do not alter 

 the thickness of the lines. But if we pass from metals to the 

 metalloids, then certainly one is prepared to go on with tlie pro- 

 fessor to any extent. I can show you how true his statement is 

 photographically. There is considerable interest attached to the 

 question whether there is or is not any chlorine in the sun's outer 

 atmosphere. I have endeavoured to settle this question, con- 

 trasting the absorption chlorine spectrum with the solar spectrum; 

 different thicknesses of chlorine have been em])loyed. It seems 

 that, if we take the metalloids, the absorption of a small thick- 

 ness often takes place in the violet porti^'U of the spectrum 



Now can these results be harmonised ? Here I acknowledge 

 we tread on very difficult ground, and with our present knowledge 

 it would be perhaps best to say nothing ; but I am not sure that 

 this would not be scientific cowardice, so I will ask, under all 

 reserve, wliether the following explanation may not be a probable 

 one? With metallic vapours the lines, though not widened as 

 they are widened by great density, are certainly darkened, but all 

 the lines are not visible — only the longest, generally. Now if we 

 assume that the channelled space spectrum of the metalloids is 

 really, even where it appears continuous, built up of lines,* then 

 the darkening of these lines by greater thickness will not only 

 make those darker that we see with a small thickness but bring 

 others into visibility; and if this goes on till we have a very great 

 thickness we may have an immense difference in the appearance 

 of the spectrum. 



11. Sonic of the vibrations are very closely connected -iviih otkei-s, 

 as evidenced by repetitions of similar givups of lines in different 

 parts of the spectrum. 



_ Here we are brought face to face with a revelation of the 

 vibrations of particles, which, if I am not mistaken, will be made 

 much of by the mathematical physicist in the future. 



I will content myself by giving two or three striking instances, 

 first noticed by Mascart. You will see that the longest line 

 is at work in all of these. 



In sodium we may say that the longest line is double ; I refer 

 to D' and D". All the lines are double. 



In magnesium the longest line is a triple combination. This is 

 repeated exactly in the violet. 



In manganese we may almost say that the same thing happens, 

 but the phenomenon is nnich more absolute in the case of those 

 particles such as sodium and magnesium, which, on other 

 grounds, I suspect to be of the simplest structure. 



12. Our hnou'ledgeof the vibrations of particles 'Liill be incom- 

 plete until the vibration is knmon from the extreme violet [invisible) 

 to the extreme red [invisibh]. In the meantime great help may 

 be got from inferences, and, in the case of metalloids at low tem- 

 peratures, from the position of their continuous absorption ; and 

 it is a question whether light may not be thus thrown upon the 

 opacity of some solid substances and the transparency of others. 



I think it not too much to say already, that in the case of some 

 gases and vapours which are ajjparently transparent it is as cer- 

 tain in some cases that their absorption is in the ultra red, as it 

 is certain that in the case of others the absorption is in the ultra 

 violet. And furtiier it is probable that this absorption is of the 

 continuous or channelled space kind — in other words that no gas 

 is "atomic" in the chemist's sense. 



13. From the fact that we have lines in the spectia of compound 

 ^ascs, it zciould be ha:a/-dous to affirm that the aggregate, 'tv/iich, 

 with the highest dissociating power we can employ, gives ns line 

 spectra, conld not be btohcn up if a still higher dissociating power 

 could be employ id. 



This proposition has a bearing on the celestial rather than on 

 the terrestrial side of the inquiry, and as my time is drawing to a 

 close I will refrain from enlarging upon it. 



There is another branch of the research I am anxious to 

 bring to your notice. I can do this better by experiment than 

 by a simple statement. 



The substance which you see here is a piece of gold leaf; it is 

 yellow, as you know, but gold is sometimes blue and sometimes 

 red. It must be perfectly clear to you, that if particles vibrate 

 the colours of substances must have something to do with the 

 vibrations. If the colours have anything to do with the particles 

 it must be with their vibrations. Now as the spectrum in the 



* Thalen's beautiful rescirches on the spectrum of iodine quite bear out 

 this view. 



main consists of red, yellow, and blue, the red and the blue rays 

 are doing something in a substance which only transmits or re- 

 flects the yellow light ; put the gold leaf in front of the lime light, 

 you will see whether the yellow light does or does not suffer 

 any change. The yellow has disappeared ; you have a green 

 colour ; the red and blue are .absent. The gold leaf is of exces- 

 sive thickne;s. What would happen could I make it thinner? 

 Its colour would become more violet. This I have proved 

 by using aqua regia. But here is a solution of frne gold, 

 which lets the red light tb.rough. Its particles are doing 

 something with the blue vibrations, or vice versi. Now 

 what is the difference — the "particular" difference between 

 the gold in this solution which is red, and that which is yellow 

 by reflected, and green or violet by transmitted light ? It is a 

 question worthy of much study, especially in connection 

 with my ninth proposilinn. Here are some more experi- 

 ments. Here is some chloride of cobalt, which is blue. I will 

 put it in this test-tube, to which I will now add water. You see 

 it turns red. I content myself by asking why it turns red ? We 

 take some chloride of nickel, which is yellow, and put it inta 

 another test-tube : we add water, and I think you will soon see 

 it turns green. First question — Why this change ? .Second ques- 

 tion — Has the green colour of this solution anything to do with 

 the red colour of the solution of gold ? 



I aslc these questions because I believe the spectroscope will 

 in time answer them. ^ 



I hope you will acknowledge that the spectroscope has to a 

 gr'eat extent vindicated the theory stated by Prof. Maxwell. 

 The question is, Has it taken us further ? Perhaps not yet, but 

 I think it will be found that what chemists pictui'e to themselves 

 as the atom, as contradistinguished from what they weigh, 

 and physicists the molecule, is that particular atom, mole- 

 cule, particle, or whatever name you may choose to call it, 

 which with high-tension electricity gives us a spectrum of lines. 

 You recollect that I said that in many of the monad metals it was 

 obtained in the first stage of temperature ; in the case of the 

 dyads and metalloids with higher stages. If the true atom be 

 that which gives a line spectrum, many anom.alies will fall to 

 the ground. These are questions the spectroscope raises. If 

 you allow that in the line spectrum an atom is at ^\ork, in chan- 

 nelled spectra and continuous spectra molecitlar aggregations, you 

 will see at once that Prof. Maxwell and others will be able to get 

 a much sharper definition of atom and molectr]e than they have 

 now ; and though atoms are little things, you ki.ow they lie at the 

 root of everything, and time spent in investigating them will not 

 be lost. 



J. Norman Lockyer 



A BOTANICO-GEOLOGTCAL EXCURSION INTO 

 THE GRAMPIANS 



T^HE Scottish Alpine Botanical Club is wont to hold a 

 -•■ spring meeting for mingled plant-hunting and con- 

 viviality in some Highland district where the Alpine flora 

 can be reached at not too great a distance from oat- 

 cakes and whiskey. The Geological class in the Univer- 

 sity of Edinburgh is in the practice of terminating its 

 labours for the winter by taking an excursion of a week's 

 duration to some part of the country where professor and 

 students can find interesting rocks, with enough of food 

 (such as it may be) to cat, and of beds, or shake-downs, 

 to sleep on. This year the two bodies, drawn together 

 perhaps as much by animal spirits as by scientitic enthu- 

 siasm, coalesced and held a conjoint gathering at Clova 

 ■ — a lonely hamlet on the Forfarshire Grampians, well 

 known to botanists for the richness of its Alpine flora, 

 and to geologists for its glacier relics and its ancient 

 metamorphic rocks. The following notes by the respective 

 leaders of the plant-seekers and the rock-hunters were 

 communicated to the Edinburgh Botanical Society on the 

 14th ult. :— 



I. Bolaiiiial Notes by Prof. Balfour. — On Friday, April 

 24, the botanists visited the lower part of Glen Fee and 

 the western side of Glen Dole. They specially examined 

 the rocks in Glen Fee, where O.xylropis eanijiestris grows 

 and along with the plant took specimens of the rock for 

 the determination of the geologists. They also visited 



