760 THE POPULAR SCIENCE MONTHLY. 



The performance of the apparatus is very satisfactory. The pho- 

 tographs show the sun's image sharply defined ; even small spots are 

 seen. When the sky is free from clouds, hut presents a whity appear- 

 ance from the large amount of scattered light, the sun's image is well 

 defined upon a uniform background of illuminated sky, without any 

 sudden increase of illumination immediately about it. It is only when 

 the sky becomes clear and blue in color that coronal appearances 

 present themselves with more or less distinctness. [Several negatives 

 taken during the summer of 1883 were shown on the screen.] In our 

 climate the increased illumination of the sky where there is a back- 

 ground of coronal light is too small to permit the photographs which 

 show this difference to be otherwise than very faint. A small increase 

 of exposure, or of development, causes it to be lost in the strong pho- 

 tographic action of the air-glare. For this reason, the negatives should 

 be examined under carefully arranged illumination. They are not, 

 therefore, well adapted for projection on a screen. [A negative taken 

 with a whity sky showed a well-defined image of the sun, with a sen- 

 sibly uniform surrounding of air-glare, but without any indication of 

 the" corona. In the case of the other negatives exhibited, which were 

 taken on clearer days, an appearance, very coronal in character, was 

 to be seen about the sun.] 



On May 6th the corona was photographed during a total eclipse 

 at Caroline Island by Messrs. Lawrence and Woods. This circum- 

 stance furnished a good opportunity of subjecting the new method to 

 a crucial test, namely, by making it possible to compare the photo- 

 graphs taken in England, where there was no eclipse, with those taken 

 at Caroline Island of the undoubtedly true corona during the eclipse. 

 On the day of the eclipse the weather was bad in this country, but 

 plates were taken before the eclipse, and others taken later on. These 

 plates were placed in the hands of Mr. Wesley, who had had great 

 experience in making drawings from the photographs taken during 

 former eclipses. Mr. Wesley drew from the plates before he had any 

 information of the results obtained at Caroline Island, and he was 

 therefore wholly without bias in the drawings which he made from 

 them. [Photographs of Mr. Wesley's drawings were projected on the 

 screen, and then a copy of the Caroline Island eclipse photograph. 

 The general resemblance was unmistakable, but the identity of the 

 object photographed in England and at Caroline Island was placed 

 beyond doubt by a remarkably formed rift on the east of the north 

 pole of the sun. This rift, slightly modified in form, was to be seen 

 in a plate taken about a solar rotation period before the eclipse, and 

 also on a plate taken about the same time after the eclipse. The gen- 

 eral permanence of this great rift certainly extended over some months, 

 but no information is given as to whether the corona rotates with the 

 sun. For from the times at which the plates were taken, one about a 

 rotation period before and the other a rotation period after the eclipse, 



