Total Solar Eclipse of 1900 (May 28). 353 



Date. Sun's H.A. Obs. decl. Tab. dec!. O C. 



May 22 -3-0 +2CT17' +20 20' -5' 



Observation with level - 1 



May 29...... -1-0 +21 36' +21 35' +1' 



Observation with level - 1' 



On the present occasion the coelostat was not blocked with wood as 

 in India ; but it was found liable to slight vibration, and a firmer sup- 

 port should l)e provided for future eclipses. 



15. Tilt of Mirror. The time available for preparation was so fully 

 occupied that no special observations for tilt of the mirror were made, 

 but in India there was found to be no appreciable tilt. 



16. FocMssing of Telescopes. The method adopted for the photohelio- 

 graph objective and magnifier was that described in the Report on the 

 Japan Expedition.* The position found was very close to that found 

 in previous expeditions. The object glass was unscrewed a quarter 

 turn, i.e., 0'02 inch, differing 0'02 inch from the position in 1898, as. 

 indicated by a wooden gauge. 



The polariscopes were focussed on a distant view (a clear view of 

 7 or 8 miles across the bay was on this occasion available) through 

 blue glass. 



The portrait lens was first focussed by blue glass, and then three 

 photographs of the distant view were obtained, which gave the focus 

 sharply. 



A focussing eye-piece made in blue glass, kindly lent by M. Trepied,. 

 4 was found very useful. I do not know whether this simple and con- 

 venient apparatus is well known ; it is made by Hermagis, of Paris. 



17. Programme of Observations with Double Tube. The six slides of 

 the double tube camera were filled with " Rocket " plates ; four of 

 them only were to be used during totality, the others being available 

 for supplementary short exposures if time should allow. As it turned 

 out, there was no time for more than the four, and the others were; 

 exposed just after totality. The actual exposures were as below : 



Time in beats from 



Exposure commencement Time in 

 No. of slide, in seconds. of totality. seconde. 



1 1 67* 56 



2 5 1318 1217 

 (Setting of Savart and slit between these.) 



3 19 3151 2948 



4 5 5560 5257 

 End of totality 66 62 



5 1 6869 6465 



6 1 75-76 7172 



* ' Monthly Notices, E.A.S.,' vol. 57, p. 105. 



