ASTRONOMICAL AND METEOROLOGICAL PHENOMENA. 261 



•we are never certain of having a dipping-needle free from special 

 ■error." 



The Report then refers to the rating of chronometers, the business 

 of which had been very laborious during the past year. At one time 

 there were about 210 chronometers in the Observatory.* 



TOTAL ECLIPSE OF THE SUN, JULY 18, 1860. 



The most important observations of the Great Solar Eclipse of 

 July 18, were obtained by the Expedition organized by the Astro- 

 nomer Royal, who (says Mr. Warren De La Rue) took overy oppor- 

 tunity, at successive meetings of the Astronomical Society, and by 

 correspondence, to promote a complete series of observations of the 

 eclipse. " As theresult of the several discussions which were raised, 

 the requisite observations became fairly taken' up ; moreover, as the 

 astronomers who had charged themselves with them distributed 

 themselves over a considerable extent of country, every possible 

 contingency to ensure success was provided for. For the most part, 

 the expedition was favoured with good weather on the day of the 

 eclipse, and results were obtained which tend to throw considerable 

 light upon, and possibly at once to set at rest, the question whether 

 the luminous prominences and corona visible on the occasion of a 

 total eclipse belong to the sun, or whether they are occasioned by the 

 deflection and diffraction of the light of the sun's photosphere. 



" As the most interest attaches to the few minutes of totality, I 

 shall confine myself to the phenomena observed at and near this 

 •epoch. 



" Some minutes before the totality I distinctly saw the whole of the 

 lunar disc, and a luminous prominence on the east of the zenith. 

 This was quite visible, while the sun's image was reflected by a glass 

 surface fixed at an angle of 45°, in the e3 r epiece, and the intensity of 

 its light consequently much diminished. The upper surface of the 

 glass diagonal reflector I had, however, silvered to the extent of 

 one-half, and, as I brought into action the silvered half just previous 

 to totality, I perceived a large sheet of prominences on the east. A 

 little to the east of the zenith a brillfant cloud, quite detached from 

 the sun, and at some distance from the moon, came into view. 

 This detached cloud did not escape the notice of other astronomers; 

 the Astronomer Royal, and I believe others also, observed the cloud 

 and prominences before the complete obscuration of the sun's disc ; 

 and Dr. Winnecke, who, with M. Struve and M. Oom, was at 

 Pobes with the Astronomer Royal, saw them some minutes after the 

 totality. The brilliancy of these prominences was wonderfully great, 

 and far exceeded that of the corona. They were not uniform in tint, 

 and, to my eye, they did not in general present a red or rose colour ; 

 two, however, had a decided but faint rose tint * much detail was 

 visible in the protuberances both of light, shade, colour, and con- 

 figuration. The side towards the sun was not brighter than the 

 opposite side ; but in some cases the more distant portions of the 



* How Chronometer are rated in the Observatory is described in an able 

 paper contributed to Stories of Inventors and Discoverers. 



