ASTRONOMICAL PHENOMENA AND PROGRESS. 



uted to be PUUpkieol Jfayaafa*. of Feb- 

 ruarv. Mr. J. Norman Loekyer refers to the 

 -Jjii-t, obtained by Dr. Frankland and him- 

 to the thickening and thinning of 

 __ lines by pressure, and the disappear - 

 i of certain lines, where the method em- 

 ^ud by them since 1869 is used. This 

 method oonstats of throwing an image of the 

 |Uhi jnurrs to be examined on the slit of the 

 spectroscope. The application of t!,U i neth.nl 

 enables the phenomena to be belter stndied. 



. 



the BMUlUe spectrum being already separated 

 frosa tha speotmm of the gaMoat medium, 



through which the electrie spark passes. Pfco- 

 tographs of the sparks taken In air, between 

 sine and cadmium, an.l sine and tin, accompany 

 the paper, showing that when speotn of the 

 vapors, given off by electrodes, are stndied in 

 this manner, the vapors dose to the electrode 

 give line* which disappear from the spectrum 

 of the Tspr at a greater distance l>..m th.- 

 leetrode, so that there appear to be long and 

 short RMS in the spectrum. In some cases 

 the spectra of the metals, inclosed in tubes, 

 and subjected to a continually decreasing press- 

 ure, hare been observed ; and it is noticed that 

 the lines gradually disappear as the pressure 

 is reduced, the shortest lines disappearing 

 first, and the longest line* remaining la*t \\-\- 

 We. Mr. Lorkyer explains at some length 

 bow these obearrations apply to the solar 

 syiitniu. and deduce* from them the presence 

 f tine and aluminium (and possibly strontinm) 

 



C*n*al Atmt*pk*r / (JU AM. At 

 the Bordeanx meeting of the French Associ- 

 don for the Advancement of Science, M. 

 finsira gave in full his view* of this su 

 obtained from bis observations of the total 

 eellpeaoB December 11 1971, seen from Shoo- 

 lor. Hindostan. He concludes that the coro- 

 nal medium U self-lighted, in great part at 

 least, and that it contains incandescent hydro- 

 Its*, but that it also exhibit* the presence of 

 raisetsJ solar light. The two analyses, spec- 

 tral and poUriaoople. agree as to this double 

 origin of the eoronal light, and all observa- 

 tions oniu in demonstrating the existence of 

 Ibis circumsolar medium. This medium is 

 distinguished, by its temperature and ita den- 

 sity, from the chromosphere, of which the 

 Haiti, moreover, U perfectly distinct. He pr- 

 poaea tret, tbe name of " eoronal envelope," or 

 "coronal ataaosphere," to remind us that the 

 luminous phenomena of the eorona owe to it 

 their nricin. M. Jansaan concludes his paper 



The 4ssMHf at the eemnal atmosphere tnu.t > 

 snsiiiliilj rr. In fcn. it b known that the spse- 

 rm f the saiosmejihus, w Its svpertor psrto, U 

 that ef s krdrafM mdiMi SMlinVslr ranted; 

 , ss HM esresiai ssflM. aesordmg to th. 



> "f Mw ipisMaay eayM to b *ren mtnitsly 

 , we see how rsr* tUs medium mu-i be, 



' -7 . 



> *f sMasss as only some 



- 



trsrred the coronal stmonhere, and yet, notwith- 

 standing the ligbtneu of their mus, they did not 

 i.ll int.. the sun. 



I ihall add here, ss to the constitution of the coro- 

 nal atmosphere, a few idea* which do not 

 flow from my oWi-rations, but which appear 

 very probable, but upon which the future uiui- 1 

 i. -jri>' 



1 said, a pro/tot of the observations in th. 

 that the corona was shown at Shoolor witli :i i -nn 

 almost square, and that it was distingu'whed by 

 gunntic dahlia-like petals. It is a fact that in each 

 eclipse the figure of the eorona has often varied ; it 

 has exhibited the most eccentric appearance-. I have 

 no hesitation In saying that this medium, now m- 

 contestably reeognued, and which I propose to name 

 the 1 ' eoronal atmosphere," very probat.ly does not 

 represent the whole of the aureole which is seen 

 during total eclipses. It is quite credible that IT- 

 t'-n- of the rings or trains of the oosmioa] matter 

 .wine visible, and thus tend to oomplioate thu 

 fltrure of the corona. It belongs to future 

 iii-tru.-t us on this point. But, with refrard tu the 

 coronal medium itself, there U no doubt that it pre- 

 sents singular forms, which convey but little idea of 

 an atmosphere in equilibrium. Moreover, I am in- 

 clined to a.liuit that these appearances are produced 

 by trains of very luminous and dense matter from 

 the superior layers ploughing this troubled medium. 

 Th.- protuberant jets, which carry the hydrogen to 

 such great heights, must have a peculiar intt 

 upon this coronal medium, whose d.-nsity is .[nit.: 

 c >m|...rable to that of the coroetary u> 



It i. then, very probable that the coronal atmos- 

 phere, like the chromosphere, is very much ngr 

 an.l that it changes its shape very npi.lly. whloh 

 will ezpUin how it presents different appearances 

 every tune it has been obsen 



To rrpest: I have been able to establish at Slioo- 

 lor, by trustworthy and consistent tlmt 



the solar corona presents tin- 



of incandescent hydrogen ga. tlmt tliin very rare 

 medium extends to very variable distance* fr.un tin- 

 sun, from half a radius of the sun to about double 

 that at certain points; l.m 1 /m- tl-s.- fijur. s ..nly 

 as results of an observation, not ns di-finitive. It is 

 quite certain, moreover, that the height of the ooro- 

 na must be necessarily variable. 



Variation in the Diameter of the Sun. 

 Father Ser-rhi him reduced a series of observa- 

 tions ,in tin- dinmctcr of the sun. extending 

 from January 18, 1871, to January 'Jl. 1 S 7'2, 

 maile by his assistant P. Rosa, Chronographio 

 transits of the sun were taken over nineteen 

 flxed threads and one movable thread, thus 

 giving twenty transits for each limb of the 

 sun. The probable error of an observation 

 ilidm-ed from the twenty threads was <>".:) 1 and 

 the minimum error was 0".5. He thus ob- 

 tained 187 trustworthy determinations, which 



were rendered comparable by havim; heen lirst 

 redocefl to the mean solar (iist.'in.-r. Thee <>1>- 

 Mrrations eorres|ninded to helio<:raphic l.-iti- 

 - compriseil between and 20 degrees. 

 While the probable error never exceeded 0".5 

 "f an arc, the isolated determinntions often 

 differe<l by .1, 4 or even 6 Becon.K i - 

 tliinks that this ilitlerem-e cannot lie attributed 

 toaoridental errot^, for they exietoil duriti: 

 oral consemtive days, and passed ins.-nsibly 

 from <me value to another; also, the compari- 

 son of these measures with analogous one- 

 niado at Palermo shows variation- suttici.-ntly 

 corresponding to those found at Rome, to 



