148 



NATURE 



\_Dec. 20, 1877 



the valley of Sto. Amaro. The path ran right up to the 

 edge and seemed to come to an end but for a kind of 

 irregular crack full of loose stones which went zigzagging 

 down to the bottom at an angle of about 70°, and we 

 could see the path down below winding away in the dis- 

 tance towards the main road to Sto. Amaro. We looked 

 over this cliff and told Mr. Wilson firmly that we would 

 tiot go down the side of that wall on horseback. He 

 laughed, and said that the horses would take us down well 

 enough and that he had seen it done, but that it was per- 

 haps a little too much ; so we all dismounted, and put 

 the horses' bridles round the backs of the saddles and led 

 them to the top of the crack and whipped them up as 

 they do performing horses in a circus. They looked over 

 with a little apparent uneasiness, but I suspect they had 

 made that precarious descent before, and they soon began 

 to pick their way cautiously down one after the other, 

 and in a few minutes we saw them waiting for us quietly 

 at the bottom. We then scrambled down as best we 

 might, and it was not till we had reached the bottom, 

 using freely all the natural advantages which Xht Primates 

 have over the Solidunguli under such circumstances, that 

 we fully appreciated the feat which our horses had 

 performed. 



*' The next part of the road was a trial ; the horses were 

 often up nearly to the girths in stiff clay, but we got 

 through it somehow, and reached Sto. Amaro in time to 

 catch the regular steamer to Bahia," 



And here is an uncommonly good anecdote about a 

 parrot : — 



"At Sto. Amaro a line of tramways had lately been 

 laid down also under the auspices of our enterprising 

 fiiend, and we went down to the steamboat wharfs on 

 one of the trucks on a kind of trial trip. The waggon 

 went smoothly and well, but when a new system is started 

 there is always a risk of accidents. As the truck ran 

 quickly down the incline the swarthy young barbarians, 

 attracted by the novelty, crowded round it, and suddenly 

 the agonised cries of a child, followed by low moanings, 

 rang out from under the wheels, and a jerk of the drag 

 pulled the car up and nearly threw us out of our seats. 

 We jumped out and looked nervously under the wheels 

 to see what had happened, but there was no child there. 

 The joung barbarians looked at us vaguely and curiously, 

 but not as if anything tragical had occurred, and we were 

 just getting into the car again, feeling a little bewildered, 

 when a great green parrot in a cage close beside us went 

 through no doubt another of his best performances in the 

 shape of a loud mocking laugh. A wave of relief passed 

 over the party, but we were rather late, and the drivers 

 expressed to the parrot their sense of his conduct, I 

 fear strongly, but in terms which, being in Brazilian 

 patois, 1 did not understand." 



In another notice we will tell of the Challenoer s doings 

 between Bahia and Cape Town, and from the Falklands 

 home, and we will also more particularly allude to the 

 general results of the scientific work she has so successfully 

 accomplished. 



{To be continued.) 



ON THE PRESENCE OF OXYGEN IN THE SUN 



T HAVE spent the greater part of last winter and the 

 ■^ beginning of this in an investigation of the spectra 

 of oxygen. My experiments will be published, I hope, in 

 another place ; but there are one or two points of more 

 immediate interest, and, I venture to think, of some im- 

 portance, which I trust you will allow me to discuss in 

 ) o jr columns. 



Prof. Draper has lately announced the important dis- 

 covery that the lines of oxygen are found to be present in 

 the sun. These lines, however, are bright, and not dark, 

 as the Fraunhofer lines. I had found that at a certain 

 temperature, lower than that at which oxjgen shows its 



well-known lines, it gives another spectrum, and it oc- 

 curred to me, when I heard of Prof Draper's discovery, 

 that if the temperature of the sun, at some point inter- 

 mediate between the photosphere and the reversing layer 

 was the same as that at which the spectrum of oxygen 

 changes, the fact that the known spectrum of oxygen 

 appears bright would be fully explained. The spectrum 

 of lower temperature, which, for reasons to be given, I 

 shall call the compound line spectrum of oxygen, ought 

 in that case to be found reversed in the solar spectrum, 

 like the remainder of the Fraunhofer lines. 



I have consequently devoted all my time during three 

 weeks to the exact measurement of these four lines, and 

 I do not think that the evidence which I am about to 

 give will be considered to fall far short of an absolute 

 proof that the spectrum is really reversed in the sun. 



Two difficulties have put themselves into the way of exact 

 measurement. The first is due to the extreme weak- 

 ness of the spectrum. The light itself is not stronger 

 than that of a non-luminous Bunsen burner ; and after 

 that light has passed through four prisms, as in most 

 of my experiments, or through seven, as in some of 

 them, there is not much of a spectrum left to be mea- 

 sured. It is only after having been in the dark for half- 

 an-hour that the eye is able to do the work, and there are 

 a good many days when the eye never obtains sufficient 

 sensitiveness to make any trustworthy measuiements. 

 But whenever my eyes were in sufficiently good con- 

 dition, my measurements agreed so well, that I have 

 no hesitation in saying that they are as accurate as the 

 measurements of the solar lines which will be found 

 by their side. The second and more serious diffi- 

 culty is due to the fact that the lines in question 

 widen to a great extent with increased pressure and in 

 such a way that the brightest part, and still more, the 

 centre of the band, is displaced towards the red. I have 

 not been able to get the lines perfectly sharp, and the 

 measurement of the centre of the band will give, therefore, 

 too high a value of the wave-length. The lollowing table 

 contains the numbers which I have obtained : — 



The first column contains the wave-length of the com- 

 pound line spectrum of oxygen. The second column 

 contains the number which has to be added or subtracted 

 from the wave-length, in order to get the edge of the lines, 

 as it is their centres which are given in the first column. 

 The third and fourth columns give the wave-lengths of 

 the corresponding solar lines as observed by Angstrom 

 (A ) or myself (S.). The greatest difference is found in 

 the line y, but even this difference only amounts to the 

 twentieth part of the distance between the sodium line?, 

 and it would require a spectroscope of very good dispersive 

 power and definition to separate two lines which would 

 be that distance apart from each other. Nevertheless 

 the amount in question is greater than the possible errors 

 of observation, and 1 believe the difference to be due to 

 the fact mentioned above, that the lines widen unequally. 

 It will be seen from the table that the solar line would 

 fall within the oxygen line, but about one-third of the dis- 

 tance between its most refrangible and least refrangible 

 ed^e. At a higher pressure the brightest part of the bard 

 lies about 5331. None of the other lines widen nearly as 

 much, and S is always perfectly sharp. Angstrom gives 

 it as an iron line, but according to Kirchhotf, the solar 

 line is composed of two lines, and separated by a distance 

 of about o'l. 



