Total Solar Eclipse of 1901, May 17-18. 223 



shutter sticking rather. Then re-set bright side of corona according to 

 picture [previously made to indicate position angle of crescent on slit], 

 and began to expose the five remaining plates in 4-prism [for second 

 ' flash ']. At 5 m 35 s I called ' Now ' to Briggs and Mrs. N. for their 

 final photographs, when I felt end of totality had come ... [I turned 

 to chronometer and waited for] W.'s signal ' Now,' which was to mean 

 the 15-seconds crescent [of returning sun]. I noted this on chrono- 

 meter, and waited further for Hobart's final ' Sixty,' which I also 

 noted on the chronometer. Called ' Cover slides,' and then went out 

 of hut and saw mackerel cloud all over the sky near the sun and 

 4 glory ' rings coloured round crescent. Sky got rapidly more clouded, 

 and clouds drifted slowly towards west. Collected notes from 

 observers." 



Summary of Exposures. Six exposures were made near second con- 

 tact with the following durations : 



1 second, 1 second, 2 seconds, 2 seconds, 2 seconds, 3 seconds. 



The seventh plate was exposed for the corona spectrum for 2 m 18 s . 

 Five exposures were made near third contact with the following 

 durations : 



2 seconds, 2 seconds, 1 second, 1 second, 1 second. 



Results. Of the twelve plates thus exposed, only four plates show 

 any impress of the light. The rest, including the exposure on the 

 corona, show nothing, though development was pressed as far as 

 possible. 



Five minutes before totality a photographic plate was exposed for 

 15 seconds to get the spectrum of the sunlight reflected from the 

 clouds near the crescent this was to serve to give standard measure- 

 ments to which the measures of the corona spectrum were to be 

 referred and a good strong negative was obtained. 



The plates at second contact are very feeble negatives, and I 

 attribute their weakness to 4 cloud. Photographs obtained with the 

 other instruments at the beginning of totality show that at least three- 

 quarters of the light was intercepted by cloud. 



The spectrum of the corona failed because of insufficient exposure 

 under the cloudy conditions. 



The plates at the end of totality, when there was certainly very 

 much less cloud, show no sign of impress of the light, and I can only 

 explain it by assuming that the image of the reappearing crescent 

 must have been set across the slit in such a way that three or four 

 more exposures than I had the means of giving were needed to catch 

 the reappearing chromosphere. Photographs obtained with the 

 objective grating show that there was plenty of light to impress the 

 plate, if only it had passed into the slit. 



