Total Solar Eclipse of 1901, May 17-18. 217 



discussion of eclipse observations were true, Dr. Downing, the Superin- 

 tendent of the ' Nautical Almanac,' having been good enough to write 

 out to us in Sumatra about this result of the discussion. It was 

 arranged that Hobart should continue the counting of seconds after 

 totality was finished, so that I might note on the chronometer the 

 instant at which the final " sixty " was called. 



The operations were rehearsed several times on the two days before 

 the eclipse, and everything went off as perfectly as rehearsals could 

 make it. In a later paragraph reference will be made to one unforeseen 

 mishap which arose from the interference of the clouds. 



7. The Day of the Eclipse. 



\Vhen the sun rose and the morning mists were dispelled on the 

 18th the day of the eclipse the conditions seemed vastly more 

 favourable than on any day in the previous week, during which it must 

 be confessed we had rather a trying time, inasmuch as sunshine was 

 needed for the final adjustment of the two spectroscopes, and it was 

 very difficult to find moments between clouds when enough could 

 be got. 



The early hours of the morning of the 18th were occupied in com- 

 pleting the adjustments, which, as it turned out, were already nearly 

 perfect, except in the case of the quartz spectrograph, as will appear in 

 a later paragraph. The clocks for driving the ccelostat and the large 

 spectrograph were finally rated, and we had gathered for a last 

 rehearsal, more for the sake of establishing confidence than of adding 

 to the instruction and drill, which had been gone through many times 

 on the two previous days. But about 1 1 o'clock, very soon after I had 

 observed the first contact, clouds began to move up from the N.E., and 

 to form round the sun, and it began to be an anxious time. I was con- 

 tent to dispense with the rehearsal in dumb-show, and thus avoided the 

 risk of inadvertent exposure of the photographic plates in the dark 

 slides, preferring to give some finishing touches to the arrangements 

 for signals, exposures, and observations. Nothing was lost by this 

 procedure, and in the actual event the programme was perfectly carried 

 out by everyone concerned, except that cloud interfered in an unfore- 

 seen way (see 11, p 221) with my operations with the 4-prism spectro- 

 graph, thus curtailing my most important exposure by 2 minutes, 

 and also involving the loss of one of the exposures with the double 

 tube. 



Fifteen minutes before totality the cloud was still hanging about, 

 and obviously forming in some places and dispersing in others. Iris- 

 coloured rings were seen round the diminishing crescent, showing that 

 the clouds were water-clouds, not ice-cirrus. Ten minutes before 

 totality I looked into one of the spectrographic instruments (see 



