8 General Results obtained from 1898 Eclipse Spectra. 



General Results and Conclusions. 



The Flash Spectrum. — Comparing the wave-length values of the flash 

 spectra given in Table I with Eowland's wave-lengths of the solar 

 lines, it is at once evident that practically all the strong dark solar 

 lines are present in the flash as bright lines ; and all the bright lines 

 in the flash, excepting hydrogen and helium, coincide with dark lines 

 having an intensity greater than three on Eowland's scale. 



The relative intensities of the lines in the two spectra are, however, 

 widely different, many conspicuous flash lines coinciding with weak 

 solar lines, and some of the strong solar lines being represented by 

 weak lines in the flash spectrum. 



This, however, applies only to the spectrum taken as a whole. 

 Selecting the lines of any one element, it is found that the relative 

 intensities in the flash spectrum agree closely with those of the same 

 element in the solar spectrum. This is particularly well shown in the 

 case of the elements iron and titanium. 



The want of agreement in the relative intensities of the lines of 

 different elements in the bright line and dark line spectra is probably 

 due to the unequal heights to which the various elements ascend in 

 the chromosphere, a low-lying gas of great density giving strong 

 absorption lines, but weak emission lines, on account of the excessively 

 small angular width of the radiating area. 



The more extensively diffused gases of small density, on the other 

 hand, give strong emission lines in the flash spectrum, and weak 

 absorption lines. 



The spectrum arcs obtained with a prismatic camera are not true 

 images of the strata producing them, but diffraction images more or 

 less enlarged by photographic irradiation. Monochromatic radiations 

 from a layer 2" in depth will produce arcs or " lines " which are as 

 narrow as can be defined by instruments of ordinary resolving power. 



The intensities of these images do not represent the intrinsic 

 intensities of the bright lines of the different elements ; the apparent 

 intensity of the radiation from an element depending on the extent of 

 diffusion of that element above the photosphere. 



But in the dark line spectrum the intensities depend on the total 

 quantity of each absorbing gas above the photosphere irrespective of 

 the state of diffusion of the different elements. 



The flash spectrum as a whole appears from these results to repre- 

 sent the upper, more extensively diffused portion of a stratum of gas y 

 which, by its absorption, gives the Fraunhofer spectrum. 



Fifteen elements are recognised with certainty in the flash spectrum 

 (No. 3), and five are doubtfully present. The atomic weights of these 

 elements in no case exceed 91. All the known metals having atomic 

 weights between 20 and 60 seem to be present in the lower chromo- 



