Notices respecting New Books. 147 



the important observation that a filling-up of close parallel lines is 

 a failing peculiar to spectroscopic vision, and that such close lines 

 throw out a haze towards each other, thatching-in the intervening 

 space. Great B with its attached band shows more distinctly the 

 excellence and value of the author's observations. The earlier 

 masses of almost black shadow (in the Eoyal Society's spectra quite 

 so) are broken up by the author's apparatus into thin lines. 



Subjects 8 and 9, with 4 plates and 14 examples, introduce us 

 to Great C, the first in order hydrogen-line. The principal point 

 noticed here is the hazy and pale character of this important line, 

 as seen in the Madeiran spectra, when compared with the blacker 

 and sharper aspect presented in the comparison spectra. The 

 author explains this by reminding us that the observation of this 

 line results from the integration of all the hydrogen activities going 

 on over all the sun's surface, and that consequently the line C could 

 have no definite outline; and he gives adequate reasons for the 

 black and well defined lines of observers with less powerful in- 

 struments. 



Subjects 10 and 11 with Plates IX. and X. illustrate "little a" 

 (alpha), or C 6 band ; and agaiu we find the author's spectra 

 showing a series of fine lines but sparingly represented in the 

 earlier maps, and of which (in a high sun) three only appear in the 

 Eoyal Society's spectrum. The high- and low-sun views of this 

 object differ essentially in strength, but not in general character. 



The indications of telluric gas-bands in nature's cold way, the 

 question of place of a red aurora-line, and of a gold line falling 

 on the very centre of intensity of this band, are referred to by the 

 author. 



Subjects 12 and 13, Plate XI., are the D or sodium-lines, so 

 well known to all spectroscopists. Angstrom's map shows one (the 

 Ni) with a high sun, and five with a low sun, of intermediate lines, 

 with the D lines black and sharp in both cases. The improvement 

 in modern observation and instrumental power is evidenced in the 

 Madeiran examples by five intermediate lines with a high sun, and 

 ten with a low. JNotably also the Madeiran examples show the 

 D lines comparatively pale and fuzzy (though not to the same ex- 

 tent as Great C), demonstrating that solar sodium (Na) enters in 

 part into the composition of the prominences. The intermediate 

 and adjacent fine lines to D 1 and D 2 are proved to be due to telluric 

 watery vapour ; and it is shown that with a really good spectroscope 

 there need be no undefined haze about them. 



From D we pass to Helium, 47,778 W. N. PI., subject 14, 

 Plate XII. The history of this line is given, and its observation 

 in the eclipses of 1870, 1871, and 1872 is referred to, together 

 with its presumed (but now disproved) detection in the aurora and 

 zodiacal-light spectra. In Angstrom's map it appears as a single 

 line marked only Fe. Eoscoe makes it single. The Eoyal Society's 

 map ignores it altogether. Vogel doubles it, but doubtfully, "as 

 it may be a tint-stone line sticking out on one side." The Madeiran 

 spectrum beautifully and sharply doubles it ; and, lastly, M. Fievez's 



