26 On 7] Argils and Jupiter's Spectrum. 



the behaviour of the known Jupiter lines as they cross these 

 zones. 



The diagram represents Jupiter and the corresponding 

 spectrum, as seen on the night of 11th December, 1869 ; the 

 general features were the same during November and 

 December. 



N P was slightly yellow and crossed by fine hair lines. 



P Q white, the brightest part of the surface. 



Q R dusky yellow. 



R T white. 



T S faintly yellow. 



P QRT dark brown. 



In the spectroscope image P Q was conspicuous through- 

 out the length of the spectrum, from its brightness. 



N P, T 8 beyond being less bright 'than P Q, showed no 

 marked peculiarity, the more refrangible end was well seen, 

 probably somewhat absorbed, but of this there was no 

 certain evidence. 



On Q P the absorption at the more refrangible end was 

 strongly marked, gradually fading away to about P, from 

 which point Q, R were seen separately with a spectrum 

 between them of nearly the same brightness as the cor- 

 responding part on the polar segments. 



* P was readily seen throughout the spectrum as a dark 

 line. 



* T was conspicuous only at the red end. 



The absorption lines, especially 914, were narrowly watched, 

 but gave no certain indications ; the narrowness of the dark 

 belts was unfavorable to the inquiry, so that with respect to 

 these the negative evidence is of little weight, but the north 

 and south segments and the zones between the dark belts 

 were sufficiently wide to afford an opportunity of detecting 

 any marked peculiarity in the spectral line as it crossed them. 



Somewhat contrary to expectation, the line retained an 

 apparently constant character throughout. 



We are therefore led to infer that the light from the 

 different parts of the visible surface had passed through not 



* On some of these belts a greenish and occasionally a reddish tinge was 

 suspected. 



