284 On Physical Observations to be undertaken in India, [Mar. 5, 



August in the present year will occur a total solar eclipse of nearly the 

 greatest possible duration. This eclipse will be visible in India, but else- 

 where only in parts of the earth which are comparatively uncivilized or 

 difficult of access. The subject was accordingly taken into consideration 

 by the Committee ; and both objects are embraced in their report, which is 

 here appended. 



Report of the Committee on Mr. Hennessey's Letter concerning 

 Astronomical Observations in India. 



*'In making a selection of subjects to which they suggest that Mr. 

 Hennessey's attention might advantageously be directed, the Committee 

 have borne in mind that that gentleman's professional duties necessarily 

 occupy the greater part of his time and attention. They have therefore 

 abstained from recommending researches which, though desirable in them- 

 selves, would require for their successful prosecution that the observer 

 should devote his main attention to them, or which, though less laborious, 

 are of such a nature as to admit of being equally well carried on elsewhere. 



§ 1 . The determination of the order of brightness of the fixed stars 

 by the method of sequences, as described by Sir John Herschel in his Cape 

 Observations, is one for which the extraordinary clearness of atmosphere 

 described by Mr. Hennessey offers peculiar advantages, and which, losing 

 absolutely nothing in value by being taken up in a disconnected manner, is 

 eminently suitable for leisure hours. It requires the use of a good star 

 map, but no apparatus. The peculiar clearness of atmosphere at Mussoorie 

 does not, it is true, extend over a very large part of the year ; but by 

 making observations sometimes in the early part of the night, sometimes 

 towards morning, a large part of the heavens might be brought under 

 scrutiny without including stars too near the horizon to give trustworthy 

 results — more especially as favourable nights might occasionally occur at 

 other times of the year. The time at which the comparison of two stars 

 was made should always be noted, in order to render it possible subse- 

 quently to make a correction for zenith-distance. 



" When numerous observations taken on different occasions have been 

 compared, should any particular star be found to exhibit unusual discre- 

 pancies, giving rise to the suspicion that it might be a periodic star, such 

 star would naturally claim special attention, and should be frequently 

 observed in comparison with a few selected stars near it in brightness, with 

 a view to test its periodicity — and in case of confirmation to determine the 

 period, and maximum and minimum brightness. 



§ 2. It would be well if Mr. Hennessey would also watch the zodiacal 

 light, after sunset about the months of April and May, and before sunrise 

 at the opposite time of year, with a view to defining its form and extent, 

 and also noticing anything which may be held to indicate whether it be 

 lenticular or annular. 



"A rough spectroscopic observation of the object, if the light be not 



