Notices respecting New Books. 



53 



has been placed within easy reach of English readers. Great is the 

 advantage of referring to original writings in all matters of science 

 and exact information. Yet the student rarely has access to the 

 publications of foreign learned societies. This particular memoir, 

 too, seems almost indispensable to every spectrum-observer ; for it 

 contains the beautiful map of the solar spectrum, and the corre- 

 sponding tables, upon the construction of which the Professor has 

 spent so much labour, and so much also that is more rare and pre- 

 cious. Just as the astronomer must have his charts and catalogues 

 of stars in order that he may identify objects known to former ob- 

 servers, and interpolate his own discoveries, so the spectrum-observer 

 must have this map of the spectrum at his elbow. 



The portion of the spectrum represented in these 

 maps extends from the line D to some distance beyond 

 the line F, occupying a length of about 4 feet. The 

 completion of the work between the lines A and G 

 is delayed by the unhappy failure of the Professor's 

 eyesight. The following small fragment, less than 

 ^Jj-Q-th part of the whole, will serve as a specimen of 

 the maps ; it represents the commencement at the 

 remarkable double line D. 



The Professor has also tabulated his results ; and 

 the following is the part of the Table corresponding 

 to the figure. 



D 



101 



100 



Col. 1. 



2. 



3. 



4. 



1000-0 



1 



a 





1000-4 



1 



a 





1001-4 



1 



a 





1002-8 



6 



b 



Na 



1005-0 



2 



b 



Ni 



1006-8 



6 



b 



Na 



1011-2 



3 



a 







! 



^ r a 



Z n 



»» 



Here we have in col. 1 the distance of the linefr om the commence- 

 ment of the scale, and, by difference, of course, from the adjoining 

 lines ; in col. 2 the darkness of each line according to the scale of 

 numbers 1, 2, 3, 4, 5, 6 ; in col. 3 the breadth of each line accord- 

 ing to the scale a, b, c, d, e,f, g ; and lastly, in col. 4 the symbol 

 of the element in whose spectrum is found a corresponding bright 

 line, — the inference, as afterwards shown, being that this element 

 exists in the sun's atmosphere. Prof. Kirchhoff proposes that each 

 line should be referred to by its number or position on the arbitrary 

 millimetre scale which he has adopted : thus the two lines of Fraun- 

 hofer's line D would be called 1002*8 and 1006 - 8 ; and Fraunhofer's 

 b consists of 1633*4, 1648'3, and 1655'0. It is a great advantage 

 of this proposed mode of reference, that it admits of the interpolation 

 of the indefinite number of finer and almost nebulous lines which any 



