DR L. BECKER ON THE SOLAR SPECTRUM. 135 



the time and meteorological notes by the Tables I. and Ia. The second line of figures in 

 the heading gives the elastic force of vapour in units of 0*01 inch, while the third line 

 shows the column of atmosphere (f-^) traversed by the light in units of that in the zenith 

 (comp. p. 86) ; f 2 may be interpolated from the table on p. 86 with argument /^ The 

 notations d, b, i have the same meaning as above. B and E indicate the beginning and 

 end of a series. 



Although the printing of the single observations of intensity demands much addi- 

 tional space, we trust that this will be compensated by the advantage they will afford 

 in later investigations. They may serve as a check on the values adopted, and enable 

 spectroscopists to consult the intensities of lines suspected to be of telluric origin. 



Table VII., on p. 100, may give an idea of the distribution of the lines with regard to 

 their intensity in different parts of the spectrum. 



The Maps. 1 



The maps are the graphical reproduction of the first three columns of the Catalogue, 

 and they are only intended to facilitate the identification of the lines with those given in 

 other maps. The main object of our work was the identification of the telluric lines, 

 which could only be done efficaciously when observing the sun close to the horizon. Rapid 

 observing was necessary ; we therefore dispensed with noting the definition of the edges 

 of lines and the various degrees of paleness in lines of the same breadth, &c. 



Of the two spectra the top one refers to the second column of the Catalogue, and the 

 lower one to the third column. The scale is in terms of oscillation frequencies (-£-) but 

 for the convenience of comparing with other maps the positions of the full wave-lengths 

 expressed in 10" 6 mm. are marked by a dot. 



The intensities of the lines are represented by the breadth of the lines only, with the 

 exception of the two lowest classes of the scale, which are distinguished from intensity 3 

 by the length of the lines. In choosing the breadth for the different classes we were guided 

 by the distance of close double lines. The notes below the spectra are a reproduction of 

 those given in the Catalogue. Lines of possibly telluric origin are not mapped in the 

 lower spectrum but their intensity is stated below the telluric spectrum. Double lines 

 which have been once separated are mapped as single, and their distance is stated at the 

 foot of the line in units of the distance between the lines of the scale ; thus d.3 stands 

 for a double line whose components are 0'3 of the interval of the lines of the scale apart. 



Postscript. 



This memoir was on the point of being presented to the Royal Society of Edinburgh 

 when we received the third volume of the Nice Observations, 2 with the late M. Thollon's 



1 The maps have been reproduced by photo-lithography, and are about one-fourth of the size of the original drawings. 

 It will be noticed that the faintest lines are far from continuous in the lithographs, but as it was found impracticable 

 to make good this defect without altering the breadth of the lines, they are left untouched. 



2 Paris, 1890. 



