A. MATHEMATICS AND ASTRONOMY. n 



experieuced a total solar eclipse on the 23d of May, 1221, 

 while traveling along the right bank of the Kerulun River. 

 If the exact time and the place of the totality can be derived 

 by Dr. Bretschneider from the Chinese record at liis disposal, 

 we shall have here one more contribution to our exact knowl- 

 edge of the relative movements of the sun, earth, and moon. 

 17 C, XXL, 1875,373. 



TOTAL SOLAB ECLIPSE OF DECEMBER 11, 1871. 



The government of India equipped an expedition, under the 

 direction of Colonel Tennant, K. E., to observe this eclipse, 

 and the results of the observations by Colonel Tennant, Cap- 

 tain Herschel, Mr. Hennessey, and others, are printed in the 

 Metiioirs of the Iloyal Astronomical Society (vol. Ixii.), ac- 

 companied by four j^lates reproduced from photographs near 

 totality. Spectroscopic as well as photographic records were 

 made, and the polariscope was also employed. From these 

 data Colonel Tennant's conclusions are derived, which he 

 states as below ; 



"The following, then, seems to bo the constitution of our 

 sun. There is a nucleus which gives out continuous white 

 light, like solid or liquid bodies, and even dense gases; sur- 

 rounding this is a layer of heavy vapors, intensely heated, 

 but far less so than the nucleus; in which, if a state of equi- 

 librium could exist, the heavier vapors would be lowest. 

 Above this is a layer of hydrogen of very slight density, 

 accompanied by that gas which gives the line D3. Still 

 farther up these gases, in a cooler state, become mixed with 

 what gives out the green line K 1474, and lastly that alone 

 seems to remain. . . . We do not know any thing of the 

 substance producing the chromospheric line D3. Professor 

 Respighi's observation at Podoocotta would go to show that 

 it is inseparable from the hydrogen of the chromosphere. 

 The substance, however, producing the green line K 1474 is 

 one of the most interesting. We not only meet with evidence 

 , of its existence in the sun, but when the higher layers of our 

 own atmosphere are reached we find at the great height at 

 which auroras take place a substance which gives out a light 

 apparently identical. Angstrom and Kirchoff have assigned 

 the power of giving this line to the vapor of iron ; but it 

 seems nearly impossible that at the low temperature which we 



