1867.] 



Presidenfs Address. 



169 



with the two surviving members, Dr. Robinson and Mr. De la Rue, and, 

 in agreement with their recommendation, have named the present Earl of 

 Rosse as their associate. 



The year 1868 will be signalized by the occurrence of a total solar 

 eclipse of almost the greatest possible duration, affording therefore more 

 leisure than usual for such observations as can only be made during the 

 brief interval of the totality. The total phase will be visible in India, but 

 elsewhere only in countries practically unavailable. Recent observations on 

 the spectra of the heavenly bodies render spectroscopic observations of the 

 red protuberances and of the corona a matter of peculiar interest at 

 the present time. The President and Council have therefore considered 

 how far they might contribute to a full use of so rare an opportunity in 

 regard to these more especially j)7i^sicaj^ phenomena. 



Having already experienced, in the case of the pendulum experiments 

 in India reported in my last year's Address, the advantage of acting in concert 

 with the distinguished officer who now holds the post of Superintendent of 

 the Great Trigonometrical Survey, Colonel Walker of the Royal Engineers, 

 and having ascertained his readiness to charge himself with the practical ar- 

 rangements which would be required for the observation of the eclipse, the 

 President and Council determined on employing a portion of the Parlia- 

 mentary grant placed at their disposal for the present year in the prepara- 

 tion of the necessary instruments, consisting of a telescope of five inches 

 aperture, by Messrs. Cooke and Sons, mounted as a portable equatoreal 

 with clock movement, and provided with a star spectroscope ; and as 

 clouds might interfere with the observations with this instrument at the 

 critical moment, they have added four direct spectroscopes for observing 

 the general character of the spectra of the red protuberances and the 

 corona, and have entrusted them to Colonel Walker, to be placed in the 

 hands of different observers. 



It has happened fortunately that a son of Sir John Herschel, an assis- 

 tant in the Trigonometrical Survey, was about to return to India from 

 leave of absence in this country, and, being applied to, expressed his 

 readiness, subject to the approval of Colonel Walker, to undertake any 

 desired share in the observations, and to make himself acquainted with, 

 and receive instruction in, the use of the instruments before his departure, 

 as well as to take charge of their conveyance to India. This arrangement 

 having received the cordial approval of Colonel Walker, has been duly 

 proceeded with, and Lieutenant Herschel with the instruments is now on 

 his way to India. 



Mr. Hennessey, First Assistant on the Indian Trigonometrical Survey, 

 having expressed in a letter to the President his wish to render available 

 for scientific researches, not incompatible with his professional duties, his 

 residence for great part of the year at the elevated station and in the clear 

 atmosphere of Mussoorie (7000 feet above the sea), his offer, which had 

 received the cordial sanction of Colonel Walker, has been embraced : 



