It may interest our readers to know that the party of scientific men, with their assistants, forming the English Eclipse Expedition, left Portsmouth, on Tuesday, in the Urgent, to proceed to Cadiz, Gibraltar, and Oran, to observe the coming eclipse.
The expedition is divided into three parties, who will be stationed at Cadiz, Gibraltar, and Oran, on the northern coast of Algiers.
The series of observations to be taken may be classified, as follows : – Spectroscopic, photographic, observations of polarisation, and the determination of the shape and extent of the corona, by the unaided vision, or with the assistance of a telescope.
The spectroscope observations will be mainly directed to the corona.
The photographic results will (should the weather be fine) probably be of very great value, as every care has been taken by Lord Lindsay, who goes to Oran, and Mr. Brothers, of Manchester, who most likely goes to Gibraltar, I hat their instruments shall be, together with their chemicals, in the most perfect order.
The polariscopic observations will be of the greatest possible interest, for it is the first time that anything like an organised series of observations in this department has been attempted.
The instructions issued to the polariscopic party are divided into five heads, and each observer is to take one the first is to notice if there is any polarisation of the corona the second to differentiate, if possible, between the corona and the luminous atmosphere surrounding the sun – the possibility of this observation depends on the light of the corona being strongly polarised; the third, to use the polariscope on the streamers.
It has been supposed by some that the polarisation observed in the corona was due to the secondary illumination, in other words, to the illumination produced by reflection from clouds, &c., towards the horizon. Now, the fourth observation is intended so far as possible to eliminate this effect so as to be able to examine the corona, as we might say, au naturel.
The construction of corona will be particularly looked after by those with plain telescopes. The Americans have stated that during the eclipse of 1869 the shape cf the corona was such as would be produced by the apparent overlapping of streams of light in the shape of Gothic arches. This is a point which will also receive attention.
The Aberdare times, 1870