1878.] Analysis in connexion with the Spectrum of the Sun. 165 



taining calcinm in such small quantities as not to show any traces of 

 the H lines. 



" How far this and similar variations between photographic records 

 and the solar spectrum are due to causes incident to the photographic 

 record itself, or to variations in the intensities of the various mole- 

 cular vibrations under solar and terrestrial conditions, are questions 

 which up to the present time I have been unable to discuss. 



An Objection Discussed. 



I was careful at the very commencement of this paper to point out 

 that the conclusions I have advanced are based upon the analogies 

 furnished by those bodies which, by common consent and beyond 

 cavil and discussion, are compound bodies. Indeed, had I not been 

 careful to urge this point the remark might have been made that the 

 various changes in the spectra to which I shall draw attention are not 

 the results of successive dissociations, but are effects due to putting 

 the same mass into different kinds of vibration or of producing the 

 vibration in different ways. Thus the many high notes, both true 

 and false, which can be produced out of a bell with or without its 

 fundamental one, might have been put forward as analogous with those 

 spectral lines which are produced at different degrees of temperature 

 with or without the line, due to each substance when vibrating visibly 

 with the lowest temperature. To this argument, however, if it were 

 brought forward, the reply would be that it proves too much. If it 

 demonstrates that the h hydrogen line in the sun is produced by the 

 same molecular grouping of hydrogen as that which gives us two 

 green lines only when the weakest possible spark is taken in hydrogen 

 inclosed in a large glass globe, it also proves that calcium is identical 

 with its salts. For we can get the spectrum of any of the salts alone 

 without its common base, calcium, as we can get the green lines of 

 hydrogen without the red one. 



I submit, therefore, that the argument founded on the overnotes of 

 a sounding body, such as a bell, cannot be urged by any one who 

 believes in the existence of any compound bodies at all, because there 

 is no spectroscopic break between acknowledged compounds and the 

 supposed elementary bodies. The spectroscopic differences between 

 calcium itself at different temperatures is, as I shall show, as great as 

 when we pass from known compounds of calcium to calcium itself. 

 There is a perfect continuity of phenomena from one end of the scale 

 of temperature to the other. 



Inquiry into the Probable Arrangement of the Basic Molecules. 



As the results obtained from the above considerations seemed to be 

 so far satisfactory, inasmuch as they at once furnished an explanation 

 VOL. xxvin. N 



