384 SCIENTIFIC RECORD FOR 1833. 



corona indicate its variations from eclipse to eclipse, a matter of much 

 importance in solar physics. 



If tbe photographs taken during eclipses in the past twenty years 

 are compared with each other, it will be seen that the corona varies, in 

 a regular way with the state of the sun's surface, although there are 

 irregular minor charges. At the sun-spot minimum the corona is much 

 more regular than at the maximum. At the minimum there is a large 

 equatorial extension, and near the solar poles a series of curved rays. 

 At the maximum there is practically no regularity at all; the long 

 streamers go up sometimes in one direction and sometimes in another; 

 and this last year near the sun-spot maximum there was absolutely no 

 symmetry in the appearance of the corona. The transparency of the 

 streamers was most striking. One streamer can sometimes be traced 

 through another, showing that the matter, whatever it is, must be very 

 thin. The rifts start from the solar surface in an entirely irregular 

 way, with a tendency very often toward the tangential direction at the 

 lower parts of the rifts. The photographs extend about a diameter 

 and a half from the sun's limb, and a comet appears on the plates about 

 a solar diameter and a half from the sun's center. It must have been 

 very bright, as it appears clearly in the photographs. Measurements 

 seem to indicate a small shift in its position during the interval be- 

 tween the first photograph and the last. 



Turning now to the photographs taken with the camera and prism 

 in front — an instrument which gives an image of the prominences as oft- 

 repeated as there are rays in the prominence — the plates employed 

 were sensible to the infrared as well as violet rays. One prominence 

 gave a great number of lines in the ultra-violet. The fact was brought 

 out in this eclipse, that the brightest lines in the prominences are due, 

 not to hydrogen, but to calcium. Besides these and the hydrogen-lines, 

 there is the line D 3 in the yellow, and the C line of hydrogen in the red, 

 and also a photograph of two prominence-lines in the ultra-red. In ad- 

 dition to the prominences, there are visible in the photographs certain 

 short rings round the moon, which mean that at these places the light 

 sent out by the gaseous part surrounding the moon is not confined to 

 the prominences. It is, as would be expected, the green coronal line 

 which chiefly corresponds to one of those rings. This green line, K 

 1474, is a true coronal line, and is only very faintly traceable in one of 

 the prominences. 



In considering the results obtained with the complete spectroscope, 

 it is a striking fact that some of the lines cross the moon's disk, and 

 especially the two lines H and K. This proves that the calcium-lines 

 R and K were so strong in the prominences that the light was scattered 

 in our atmosphere and reflected right in front of the moon. 



The prominence-lines are very numerous; thirty such lines appear in 

 the photograph. The hydrogen-lines are there, including those in the 



