236 The Eclipse of Last December. [April, 



the most exquisitely beautiful phenomenon possible to 

 conceive, and it seems to me to have considerable theoretical 

 importance. Secchi's continuous spectrum of the sun's limb " 

 (the existence of which had been so strenuously denied) "is 

 probably the same thing modified by atmospheric glare, — 

 anywhere but in the clear sky of Italy so much modified, 

 indeed, as to be wholly masked." 



Now, with respect to the lines seen in the spectrum of 

 the corona, it is to be noted that Mr. Abbay, " observing at 

 Xeres with a spectroscope of two prisms of 45 belonging 

 to Professor Young, saw the bright lines c, D, and F, and 

 afterwards another line rather more bright than F on the 

 less refrangible side of b." But it is worthy of notice, as 

 pointed out by Professor Young, that with a hazy sky as at 

 Xeres, and, indeed, all the Spanish stations, it is impossible 

 to feel sure from the mere appearance of a line that the part 

 of the corona towards which the spectroscope is directed 

 really has a spectrum showing that line. In fact, the 

 appearance of the c line of hydrogen as far as 6' or 7' from 

 the sun, " far above any possible hydrogen atmosphere," says 

 Young, effectually demonstrates this, even if it had not 

 happened that Mr. Abbay had seen the c and F lines on the 

 moon itself. 



Fortunately, however, Professor Young has been able to 

 establish in a highly satisfactory, or rather demonstrative, 

 manner the fact that light coming from a region much more 

 than 6' or y' from the sun's limb gives the bright line 1474 

 Kirchhoff, — the very line be it noted respecting which the 

 gravest doubts had been expressed. Of the four spectroscopes 

 employed by his party, " two," he writes, " were what might 

 be called analysing, and two integrating instruments." The 

 former gave the relative brightness of the several lines in 

 the spectrum from a definite portion of the corona or 

 prominences; the other showed the relative quantity of 

 light corresponding to different bright lines when the whole 

 of the corona supplied light to form the spectrum. Now 

 the analysing spectroscope showed the line 1474 very much 

 fainter than the c line of hydrogen. " Even during totality," 

 says Professor Young, " 1474 can hardly be called con- 

 spicuous in an analysing instrument, while c blazes like a 

 red Sirius ; " and he concludes that c is at least 25 times 

 and perhaps 50 times as bright as 1474. Now in the in- 

 tegrating spectroscope the order of brightness is reversed. 

 The line 1474 is appreciably brighter than the line c, in- 

 somuch that Professor Young assigns as the numbers 

 indicating the relative brightness of these lines, 100 for the 



