62 Mr. J. N. Lockyer's Reply to some Remarks of 



for its object, as I clearly stated, the settlement of certain points 

 where our observations were not in agreement, in order that 

 other workers might employ the new method of observation 

 under the best conditions. 



I gather from Father Secchi' s communication — 



I. That he still holds to a " couche donnant un spectre continu, 

 couche qu'il considere com me la base de V atmosphere solaire, et 

 dans laquelle, il pense que s'effectue le renversement selon la 

 theorie de Kirchhoff." 



II. That he has doubts as to the importance which I attribute 

 to the widening of the F line at its base, on which Dr. Frank- 

 land and myself have founded our estimate of the pressure of the 

 chromosphere. 



III. That he also has doubts as to the changes of wave-length 

 in the hydrogen-lines, which I have asserted to be continually 

 visible both on and off the sun. 



IV. That he holds still that the line F is due to the absorp- 

 tion of some other substance besides hydrogen. 



With regard to all these points I am quite content to leave 

 the verdict to the future. I may, however, remark with regard 

 to the first point, that although I see nothing like a continuous 

 spectrum, I do see traces of reduced absorption in the exterior 

 layer of the photosphere ; and Dr, Frankland and myself have 

 proved why the absorption increases as the lower layers are 

 brought into action, as in a spot. Father Secchi has written *, 

 "Ayant examine comparativement le spectre du noyau des 

 taches et celui du bord du disque du cote interieure, je suis 

 arrive a la conclusion que ces deux spectres se ressemblent con- 

 siderablement. U enlargissement des raies constate dans le noyaux 

 se reproduit pres dubord." I do not find this; but it appears to 

 me that this is a contradiction in terms to his assertions about the 

 continuous spectrum of these regions. 



With regard to the second, in which the action of pressure is 

 in question, I again quote t : — " J'ai encore porte mon attention 

 sur la largeur des raies brillantes de la chromosphere et j'ai con- 

 state qu'en general les raies principales sont toutes trois plus 

 large a la base qu'au sommet, ce qui prouve ^influence de 

 la pression exercee par les couches superieures." This strikes 

 me as another contradiction in terms, and Father Secchi must 

 take his choice between these assertions. But I must do him 

 the justice to admit that he early thought something could be 

 made out by means of pressure experiments, for he recommended 

 that the spectrum of hydrogen sous une tres forte pression should 

 be observed, while Dr. Frankland and myself were working suc- 

 cessfully near the vacuum-point. 



* Comptes Rendus, 2 e sem. 1869, p. 41. t Ibid. 



