278 



KNOWLEDGE 



[Deoembee 1, 1894. 



In that point of view, the characteristic hydrogen 

 spectrum is particularly remarkable. It has never been 

 obtained in chemical flames, even the hottest, and although 

 thousands of attempts have been made under the most varied 

 conditious(-). On the other hand, the smallest induction 

 coil gives it easily, and, a point well worth noticing, the 

 electric arc gives it also, but feeble and with difiioulty ; so 

 that electric interference, even with a notable tension, 

 appears necessary to its formation(^). 

 . Now then, all the points of the chromosphere show this 

 characteristic spectrum of hydrogen, so that we must con- 

 clude, as Mr. Fizeau, and, I believe, Dr. Huggins do, 

 that the chromosphere is an electric flame ; or, at 

 least, this conclusion, which rests on a great number of 

 varied experiments, is by far the most probable, in the 

 actual state of our knowledge. But this point once 

 admitted, I have been somewhat puzzled for a moment, 

 because the electric flames of our laboratories have not 

 that same shape, and spring up generally between two 

 poles. Now, in the present case, where are the poles'? 



Quite naturally I have thought of the earth, which is the 

 only celestial body we know (yet imperfectly), and which 

 being a cooled sun, must, in all likelihood, present on a 

 smaller scale the same phenomena as the incandescent 

 stars do, on a larger scale. 



And I have immediately been struck with the analogies 

 between the solar chromosphere and our own atmosphere, 

 looked upon from the point of view of its electric state. This 

 odd and as yet unexplained phenomenon of the rapid 

 increase of the electric potential with the altitude(*), which 

 constitutes what is called atmospheric electricity, is general 

 for all the earth. The fall of potential, as we know, is 

 stronger in tropical regions ; stronger also, all the other 

 conditions being the same, in mountainous regions. 



Now in the solar atmosphere the electric distribution is 

 also the same, the fall of potential in each point being 

 measured by the intensity of the light set forth ; indeed, 

 the chromosphere is brighter in the region of the spots, 

 and, above all, shows very clear maxima over the faculse 

 which are just the lofty part of the surface of the sun. 

 Then both electric phenomena have the same ways in 



(2) Prof. Hartley, in a recent study on the spectrum of the Bessemer 

 (lame {Pi-oceedinijs of the Soyal Socielit, Vol. LTI., ^'^o. .337, p. 193), 

 has made this very interesting observation : " In the first period of the 

 blow, the C line of hydrogen, and apparently the F line, were seen 

 reversed during a snoir-slofiti." Xow, Prof. Hale, in the last number 

 oi Asironomii and Astro-p/ii/sics, page 771, relates this nev\' experiment 

 and adds that the fact, if substantiated, ii eontrary to the electric ex- 

 planation of the chromosphere. I have not the same opinion for several 

 reasons : — 1st, In this one experiment the rays are not brilliant, but 

 black and reversed, which is not exactly the same ; 2nd, a very strange 

 cendition, difficult to realize, the coincidence with a snow-sto m appears 

 necessary. In a snow-storm the dilferences with the ordinary con- 

 ditions are not in the comuosition of the gaseous air, which is only 

 relatively dry, but in the particular state of atmospheric electricity ; 

 so that electricity seems yet to bear a predominant part in the pheno- 

 menon. But, was snow falling on the flame ? Tlie note of Prof. 

 Hartley gives no details, and the complete discussion is therefore 

 difficult. In fact, till further experiments, I maintain my first conclu- 

 sions ; and this curious observation, such as I have understood it, 

 suggests to me only the idea to study the Bessemer flame in various 

 electi'ie fields, in conditions as similar as possible to those of a snow- 

 storm. 



(3) The intense chromosphere lines H and K of calcium confirm 

 (lie result to a certain point; very feeble in the chemical flame, 

 where Prof. Hale has recognized them, they are strong enough in the 

 electric arc, and very strong in the induction spark, according to the 

 experiments of Prof. Lockyer. The gradation is the same if we 

 notice that chemical flames are the seat of weak electro-motive forces. 

 We see that the production of these lines seems to require, as the 

 electrolysis of the saline solutions, the use of a minimum number of 

 volts ; a small number for calcium, but a high one for hydrogen 



(■t) The difference of potential between the top and the bottom of 

 the Eiffel Tower is often 10,000 volts. 



both atmospheres, and this unexpected verification strongly 



confirms the admitted conclusion. 



However, the terrestrial atmospheric electricity, the cause 

 of which is still unknown, is probably due to the evaporation, 

 the condensation and the relative motions of the atmospheric 

 gases. The same causes exist also for the sun, and in larger 

 proportions ; and one may comprehend that the effects 

 must also be more considerable. 



One single remark more and I have done. The electric 

 explanation of the chromosphere agrees very well with all 

 the mechanical theories of the sun, and especially with 

 that of Mr. Faye, which, in my judgment, best explains 

 the whole of the phenomena. Likewise, in the study of 

 the terrestrial tempests, the motions of the air, and the 

 electric variations that attend them, are generally studied 

 apart. In reality, the advancement of our knowledge of 

 the solar atmosphere is closely bound up with the progress 

 of terrestrial meteorology. y . j. . , . 



The Observatory, Paris. ^- Desl.^ndrf.s. 



S((enct Notts. 



The Christmas course of lectures, suitable for children, 

 at the Royal Institution, will be delivered by Prof. J. A. 

 Fleming, F.R.S. The subject will be "The Working of 

 an Electric Current," and the first lecture will be delivered 

 on December 27th, at three o'clock. 



Our contemporary Xature has completed its fiftieth half- 

 yearly volume. Prof. Huxley wrote the first leading article 

 in 1869, and he has also written the leading article for 

 No. 1305, vol. 51, November 1st, in which he shows how 



firmly grounded is the theory of evolution. 

 — .-♦-« — 



The Museum of La, Plata will shortly issue the second 

 part of Mr. Lydekker's memoir on the fossil vertebrata 

 of the Argentine Republic. It will be illustrated by over 

 sixty folio plates, and deal chiefly with the Edentate 

 mammals. 



Xaturi> for November 15th reproduces from La Nitture 

 some beautiful figures produced from ink, by Dr. E. 

 Frouessart. A drop of ink is allowed to dry on a slip 

 of glass, and observed under a microscope. They belong 

 chiefly to the cubic system, and the writer of the original 

 paper suggests that they are magnetic oxide of iron. But 

 this question is not settled, they may be iron-disulphide. 



Talking of " extinct monsters," it may be just as well 

 to remind our readers that the animals so humorously 

 introduced into Pi(«(/i's " Px'ehistoric Peeps,'' by the artist, 

 Mr. E. T. Read, are not in all cases founded on fossil 

 remains, though many of them are. Truly, there are more 

 things in Mr. Punch's mind than are dreamed of in our 

 geological philosophy ! 



The German Emperor has lately presented to the Berlin 



Natural History Museum a very fine specimen of a Plesio- 



saurus skeleton (the first ever found in Germany), in 



which part of the outline of the creature is preserved on 



the rock, chiefly about the tail. It has been named after 



the Emperor by Prof. W. Ct. Dames, of Berlin, who will 



in February lecture on it to the Academie. The lecture 



will afterwards be published with a plate. 

 — ^-^-* — 



[The plate representing the ''Daddy long-legs" in the Xorember 

 number of Knowiedge w.as taken from a lantern slide kindly lent 

 bv Messrs. Xewton & Co.1 



