PHOTOGRAPHS OF THE CORONA. 117 



whatsoever of this eclipse we should have been justified in 

 placing a large measure of confidence in the features presented 

 to us by the consensus of the Buxar artists. Further, it so 

 closely resembles the well-known drawing by Captain Bullock 

 of the corona of 1868, that we need have not the slightest 

 hesitation in accepting the latter as a faithful representation 

 of the eclipse of that year. 



The difference between the drawings and the photographs 

 has no doubt been chiefly due to the very simple fact that the 

 coronal streamers were too faint to be photographed in anything 

 like the time during which the plates had been exposed. 

 Though with adequate exposure a sensitive plate can embrace 

 a wider range of intensity than the eye, yet for such exposures 

 as are alone possible during an eclipse the eye has much the 

 advantage. Never until this eclipse has so long an exposure 

 been given with such rapid plates ; and had it been otherwise, it 

 is doubtful whether on any but triple-coated plates the develop- 

 ment could or would have been pushed sufficiently far to bring 

 up these faint extensions. The rapidity with which the coronal 

 light faded away was indeed known, but the necessity if these 

 outer regions were to give an impression for giving exposures 

 to correspond does not seem to have been sufficiently realised. 



The chief features shown by these long-exposure photographs 

 are four long rays. 



N.E. S.E. S.W. N.W. 



Position angle from sun's north 



pole 69 ... 235 314 



Length on plate No. 20 . . 112' 72' 119' 71' 



27 . . 126 94 162 91 



,, 29 . . 180 123 226 124 

 Length in lunar radii on plate 



No. 29 .... 11-0 7-5 13-9 7'6 



The position angle of the S.E. ray is not given, as it is very 

 nearly tangential to the sun's limb, whilst the other three rays 

 are nearly radial. The lengths given for the rays are of course 

 their apparent lengths ; their real lengths are probably con- 

 siderably greater, for we do not know in what plane they lie, 

 nor how far their apparent lengths have been diminished by 

 foreshortening ; the values given above therefore are a minimum. 



The rays in appearance are straight, narrow, and rod-like up 

 to the limits given in the above table. But their bases are of 

 an altogether different form. Each one rises from one of those 

 " synclinal structures " to which Mr. Kanyard called attention 

 in his great eclipse volume (Memoirs R.A.S., vol. xli.). Only 

 four of these structures were seen in this eclipse, and in each 

 case we now see from these photographs that they terminate 

 in one of these rod-like rays. The bending towards each other 



