William Kingdon Clifford and the eclipse of 1870

William Clifford was a member of the English Eclipse Expedition of 1870 which went to Sicily to observe a total eclipse. It occurred on 22 December 1870 and the path of totality was to cross Portugal, Spain, northern Algeria, Sicily, Greece, Bulgaria, and Ukraine. The English Eclipse Expedition set off earlier in December on the steamship Psyche planning to sail to Naples before continuing to Syracuse in Sicily. An article describing the expedition, written by William Grylls Adams (1836-1915), professor of Natural Philosophy at King's College, London, was published in the Monthly Notices of the Royal Astronomical Society in early 1871. W G Adams was the younger brother of John Couch Adams. We present extracts from Adam's article relating particularly to the contributions made by William Clifford.

The Psyche was wrecked on 15 December 1870 off Catania. Her crew were later court-martialled. The wreck was blown up in February 1871.


The Psyche arrived [in Naples] during the day [Wednesday 14 December 1870] ... and she steamed out of harbour at four o'clock. It was a peaceful afternoon, with no wind and a perfect calm sea, and the view of the bay, with Naples in the sunshine and Vesuvius sending out light puffs of steam and smoke, was very beautiful. The sea kept perfectly calm through the night, and on the morning of the 15th, after passing Messina, a meeting was held and observers were stationed. The instruments were brought on deck, and we were enjoying the scenery of the coast and of Etna when the unfortunate wreck of the Psyche cast a gloom over our Expedition and entirely altered our arrangements. It was intended that Syracuse should be the head-quarters, but now Mr Lockyer took up his station at Catania. Professor Roscoe took charge of a party to observe on the slopes of Etna, and I was asked to take charge of the Augusta Expedition. The other observers at Augusta were - Mr Brett, with a reflector for sketching the corona; Mr Burton, with a spectroscope; Mr Clissord and Mr Ranyard, for observations on polarisation; Mr Samuelson, for general observations. ...

With such an excellent practising ground as the terraces and gardens of the Benedictine Monastery, it was thought better that the Etna and Augusta observers should stay at Catania until Monday, the 19th, and practise with their instruments. As there had been no opportunity for testing the instruments, this comparison was very important, especially for all those who were to observe for polarisation; some of whom had never seen their instruments. All the observers for polarisation (including Clifford) except Mr Ranyard remained, and arranged the sets of observations to be made by each observer, so that if the weather was favourable, the determination of the polarisation of the corona should be complete. ...

On Monday, the 19th, Mr Clifford and I left Catania in a boat to go to Augusta. In consequence of a breeze from the sea we did not reach Capo San Croce until eight o'clock, and after turning it we had a strong breeze against us from the west. Twice during the evening, about half past six and again about seven o'clock, we saw a brilliant display of the aurora. It was far more brilliant than the remarkable aurora which I have seen in October, and more beautiful than any I had seen. First pink streamers shot up perpendicularly to the eastern horizon, passing across the planet Jupiter. I judged that these must have been in or near to the ecliptic. These were followed by other streamers shooting up from the north and north-east until the sky became covered with a pinkish mauve colour. ... As the evening grew darker we saw the strong phosphorescence of the sea. there was a bright glow on the drops thrown up by the oar as it struck the water, and the forms of the eddies caused by the bending of the oar were distinct and brilliantly illuminated. ...

Each observer had one of the Sappers to assist him in preparing his instruments and in recording any notes which might be necessary to make during totality. Where they were required, tables formed by driving piles into the ground and nailing planks on them were erected for our telescopes. On the 21st we were able to get our instruments into position, and the Sappers showed their skill in repairing parts of instruments which were out of order. ... It was arranged that about two minutes before totality one of the Sappers should give the time at intervals of ten seconds, and that at the last minute before totality he should begin to count continuously and give every five seconds until after totality.

Large thick clouds were flying from the west, and frequently obscuring the Sun and rapidly passing away. When the Sun was about half eclipsed, there was rather a sudden change in the light and a sudden chill was felt in our observatory. About three minutes before totality there were brilliant and very remarkable patches of red and yellow light on a cloud to the right and rather below the Sun. This cloud passed away and the Sun was quite clear. The time of totality was now very near, and a cloud from the west was threatening to blight our hopes; the band of sunlight was getting exceedingly thin and seemed to be breaking up into sections, when at the very instant the dense cloud came over the Moon and shut out the whole, so that it was doubtful whether the Moon or the cloud first eclipsed the Sun. For a full minute I could detect nothing of the Moon's disk, but moved my telescope very gradually, then the cloud became thinner, and I found the Moon still in the centre of the field. ... The Moon was again obscured entirely, but after a few seconds I again detected light of the corona near the point of emergence ... The view then became continuous and totality was over. ...

Mr Clifford observed light polarised on the cloud to the right and left and over the Moon, in a horizontal plane through the Moon's centre, and found the plane of the polarisation inclined at from 15° to 20° to the vertical. At his last observation on the Moon, when it was visible, the plane of polarisation was vertical. Mr Clifford also saw the corona near the point of emergence about the end of totality. It will be seen from Mr Clifford's observations that the plane of polarisation by the cloud was very nearly ... at right angles to the motion of the Sun.


JOC/EFR July 2015

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