70 Royal Society : — 



instance, and then from a portion silvered on the top surface the 

 instant the period of totality commenced. By its means he avoided 

 the perplexity and loss of time occasioned in unscrewing and screwing 

 portions of the apparatus at the most critical period. To these were 

 added a small transit theodolite, three chronometers, two baro- 

 meters, and several thermometers. 



The weather proved so unpropitious that it was with much dim* - 

 culty the ohjects of the party could be carried out ; and it was only 

 by using every available opportunity that even the Kew instrument 

 could be placed in position. 



The geographical position of the site of the observatory was ascer- 

 tained to be — north latitude 42° 42', west longitude 11 min. 42*7 

 sec, elevation above the mean high-water mark 1572*4 feet. 



The author made two sketches of the luminous prominences 

 during the period of totality, on paper previously ruled to represent 

 the position-lines drawn on a piece of parallel glass placed in the 

 focus of the eyepiece, which magnified about 60 times. These 

 position-lines consisted of a square calculated to exactly include the 

 lunar disk, and two external squares, one exactly one minute of arc 

 distant from the central square and from the other. The angles of 

 the squares were joined by diagonal fainter lines. The whole 

 system was moveable through an arc of 90°, and its position could 

 be read off on a graduated external circle divided from 10 to 10 

 degrees. The drawings were by chance made of nearly the exact 

 diameter of the lunar disk in the photographs (4 inches), and proved 

 very valuable in interpreting the phenomena revealed by the latter, 

 as the one could be compared by superposition with the other, and 

 the several prominences be thus identified. 



One of the prominences, situated about 30° from the north point 

 towards the east, became visible several minutes before totality, even 

 during the employment of the unsilvered portion of the diagonal 

 reflector. As the sun disappeared the author watched for the so- 

 called Baily's beads, but no such phenomenon occurred, which 

 occasioned no surprise to him, as he had always believed that it arose 

 in all probability from the atmospheric disturbance of an image 

 formed by a telescope wanting in definition. 



The author goes on to describe the various appearances presented 

 by the several protuberances, which were not all of a rose-colour, 

 and those which presented this hue were much paler in colour than 

 his previous reading had led him to expect. He is able to speak 

 with considerable certainty on this point, having before the eclipse 

 painted several colours on his drawing-paper, and was thus enabled 

 to compare these directly with the prominences by means of the 

 light emitted by the corona, it being sufficiently great and polychro- 

 matic for that purpose. The light of a lamp which was at hand 

 proved not only useless, but was detrimental in making the com- 

 parisons. There was a considerable amount of detail, both of form 

 and colour, in the prominences, which the author has shown in two 

 coloured drawings which accompany the paper ; these are founded on 



