568 REPORT— 1894. 



19. The Influence of Temperature upon the Specific Heat of Aniline} 

 By E. H. Griffiths, M.A. 



Tlie author drew attention to the fact that water is by no means an ideal 

 liquid for calorimetric purposes, its great capacity for heat rendering it unsuitable 

 for operations such as that known as ' the method of mixtures.' Again, we have 

 but little knowledge concerning the chunges caused in its speciBc heat by changes 

 in temperature, and its vapour pressure at low temperatures is sufficient to cause 

 a constant leakage of heat by the processes of evaporation. 



In all these respects aniline appears to be superior. 



The method adopted for determining the specific heat of aniline was an electrical 

 one, and the specific heat was ascertained over a range of from 15° to 52° C. The 

 heat developed by rapid stirring was balanced by heat lost by convection, conduc- 

 tion, &c., and the rate of rise at diff'erent temperatures, due to the electrical supply 

 only, was ascertained. 



The results are closely represented by the formula 



s = 0-5156 + {t- 20) X -0004 + (C - 20)- x 000002. 



The values obtained by means of this equation do not in any case differ from 

 the experimental results by more than 1 in 2,000. 



20. On some Photometric Measures of the Corona cf A^n'il 1893. 

 % Professor H. H. Turner, M.A. 



The present paper is merely a preliminary note on some measures of the photo- 

 metric intensity of the corona on photographs taken at Fundium by the British 

 expedition in April 1893. 



The measures (of density of deposit at various points on the plates) were 

 made at South Kensington by the kindness of Captain Abney, who lent me his 

 apparatus for the purpose. This apparatus has been described by him else- 

 where in detail; and here it is only necessary to remark that a beam of light is 

 divided by a plane glass plate, part being transmitted and part reflected. The 

 photograph is placed in one beam, and a ' rotating sector ' in the other. The 

 beams are then caused to illuminate two small screens placed side by side, and 

 the aperture of the rotating sector is varied until the illuminations are equal. 

 The aperture of the sector is then read, and the reading is a direct indication of 

 the density of the photograph at the particular point under examination. In this 

 note it is desired to call attention to one or two points Avhich the observations, 

 though as yet incomplete, have suggested. 



(1) I cannot help referring to the beauty and simplicity of the rotating sector. 

 The ease and accuracy of the observations are such as I was quite unprepared for ; 

 and it seems to me that the apparatus is indispensable to the astronomical 

 photographer. I look forward to making use of it in a large variety of ways. 



(2) The points examined up to the present have been distributed along four 

 radii respectively north, south, east, and west from the moon's centre. If the 

 density be tabulated according to distance from the moon's limb, the resulting 

 curves are very similar to ' error ' curves, with the maximum at the moon's limb, 

 and deviations from a smooth curve are very small. 



(3) The results for the four radii are very similar ; and the mean of the east 

 and west radii gives a curve almost identical with that for the mean of the north 

 and south radii (the means being taken to eliminate the distance between the 

 centres of sun and moon). The general form of the corona at ' maximum ' is in 

 accordance with this result, but I was not prepared for so close an accordance as 

 the figures show. 



(4) The density of the film has by no means reached uniformity at the edge 

 of the plate, even in the small scale photographs, which allow of measures up to 

 70' or 80' from the limb. It is possible that the light causing this deposit is not 



' See Phil. Ma//., 1894. 



