32 



NA TURE 



[May 10, 1883 



SIDEROSTAT. 



EQUATORIAL. 



Time. 



Before Totality 



Minutes. 



10 



9 

 8 



7 

 6 



5 



4 



3 



2 



Seconds. 



60 



40 



20 



2 



1 



Totality 

 280 

 230 

 220 

 210 

 200 

 120 

 no 

 100 

 90 

 70 



5° 

 40 

 20 



Just before end 



.-{/?(•;• Totality 



Seconds 



1 



4 



10 



Minutes 



I 



2 



3 



5 



7 



9 

 10 



Hilger. 



ref. spectrum 30 scs. 



Rowland grating. 



1st 

 order. 



2nd 

 order. 



Prismatic camera. 



Slit 

 Spectro- 

 scope.' 

 2 pnstn. 



7 prism, 

 F. 



expose & start clock 



expose 

 expose 



expose 



expose 



expose 

 expose 



expose 



expose 



Grating. 



F. Red I F. Blue 

 1st order. 2nd order. 



\ in. slide. 

 Dense 

 ptism 



expose expose 



expose 



shut 



refs. 25 



expose col. plate 



shut 

 expose gel. plate 



shut 

 expose col. plate 



shut 



expose 



expose 



expose 



run \ in, 



expose 



Ant 



expose 



1 1 1 ■ e 



shut 



10 sec. 



PHOTOHE- 

 LIOGRAPHS. 



Large 



photo- Corona camera, 

 helio- 

 graph. 



expose 



expose 



expose 



expose 

 expose 

 expose 

 expose 

 expose 

 expose 

 expose 



expose 



expose 



expose 



expose 



expose 



expose 



shut 

 10 sec. 



expose 

 expse 



expose 

 shut 



expose 1 sec. 

 20 sec. 



expose 



shut 

 expose 3 sec. 



expose 10 sec. 

 expose 2 sec. 



Lieut. Brown, and Mr. Upton, the first mentioned astro- 

 nomer being in charge, at Panama. They expected to 

 arrive at Callao on the 20th March last, and to leave 

 either in the Hartford or the Pensacola within the next 

 few days. That would give them ample time to reach the 

 Caroline Islands, and make the arrangements necessary 

 for the observation. It was the intention of Prof. Holden 

 to take the combined English and American party on to 

 Flint Island if he found that Dr. Jannscn had already 

 established his party on Caroline. This, of course, was a 

 very proper decision, as it would double the chances of 

 favourable weather. We give the time-table for observa- 

 tion supplied to the English observers, which they were 

 instructed to carry out down to its most minute detail, if 

 all the instruments were landed and set up without 

 damage. 



It will be seen that the English attack was to be en- 

 tirely photographic ; no eye observations were to be made. 

 And if all has gone well, something between fifty and 



sixty photographs may be hoped for. The table perhaps 



; requires a little explanation, which we will now proceed to 

 give. It followed from work undertaken with that special 

 object in Egypt last year, that eclipse observations can 

 now definitely begin ten minutes before totality, and end 

 about ten minutes after. With an eclipse therefore of 



; about five minutes' duration, as in the present case, the 

 work ranges over a period of live-and-twenty minutes, and 

 if the plates are as sensitive as they can now very well be, 

 it is quite easy to see that a very large number of photo- 

 graphs may be taken. The greatest interest of course at- 

 taches to the spectroscopic photographs to be taken by 



I means of a siderostat and the equatorials. As in former 

 eclipses the plates exposed in the photoheliographs will 



I secure the appearance of the corona surrounding the image 

 of the dark moon ; but on the present occasion an attempt 

 was to be made to take these photographs on a much larger 

 scale than usual, a scale of four inches to the moon's 

 diameter. Coming to the spectra themselves, we find 



