A. MATHEMATICS AND ASTRONOMY. 59 



tation of delicate appliances, but the points to whicli he 

 directed his attention were, although few, perfectly definite. 

 By circulars distributed throughout the colony, instructions 

 were communicated as to the proper methods of making 

 drawings of the corona, and several important drawings were 

 received, which are carefully studied by Mr. Stone. They ex- 

 liibit the usual marked discrepancies in most cases, notably 

 in two made by two expert draughtsmen seated side by side 

 at the same table; but Mr. Stone gives a satisfjictory explana- 

 tion of the differences here, which may serve to account for 

 similar discrepancies in former drawings. Mr. Stone sum- 

 marizes the results of his expedition as follows: 



" 1. A confirmation of Young's observation of the general, 

 or nearly general, reversion of the Fraunhofer lines in the 

 spectrum of the corona near the photosphere. 



" 2. A spectroscopic examination of the outer corona, in 

 contradistinction to the inner corona, carried to the extent of 

 rather more than a degree from the sun's centre, which has 

 proved that the spectrum of the outer corona consists of a 

 linear spectrum of one bright line, either exclusively or sen- 

 sibly, whose wave length is 5.312, with a unit of one tenth of 

 a meter, and of an ordinary sunlight spectrum with absorp- 

 tion lines. The spectrum of the outer corona has been shown 

 to fade gradually away, as the extreme visible limit of the 

 corona is approached, and not to disappear sharply, as if the 

 extreme limit of the corona had been reached. 



"3. The spectroscopic examination of the outer corona, 

 combined with the unchanged character of its principal feat- 

 ures, as seen at [three different observing stations] at intervals 

 of absolute time extending to ten minutes, and at distances 

 of more than 500 miles, proves, I venture to think, the solar 

 origin and cosmical character of the outer corona. . . . 



"4. A comparison of the drawing of Mr. Henry Ilall . . . 

 and the photographs obtained in 1869 and 1871, shows the 

 permanent character of the contraction of the inner corona 

 in a direction parallel or nearly parallel to the sun's axis of 

 rotation. The strongly marked character of the general con- 

 traction of the outer corona in the same direction may not 

 improbably ultimately lead to a similar inference in the case 

 of the outer corona also." Memoirs Royal Astrono7nical So- 

 ciety^ XL., 11. 



