February 2^th, igi^.'\ PROCEEDINGS. xix 



connecting-bonds, for the representation of a carbon molecule. 

 This is rather significant, as it suggests the constitutional 

 formulae for the three modifications of carbon. Correlating this 

 with the calorimetric measurements and relative proportions of 

 oxygen, used up in the formation of the complexes, the formula 

 for each form of carbon can be deduced. This gives also the 

 possibility of deducing the general formula for the complexes 



Mr. J. B. HuBRECHT, M.A., read a paper entitled ** Studies 

 in Solar Rotation." 



An account was given of a spectvographic determination 

 of the solar rotation, as observed at Cambridge. Photo- 

 graphs had been taken showing the displacements of the 

 absorption lines due, in accordance with Doppler's principle, to 

 motion in the line of sight of the points on the sun's limb 

 compared. The velocity of such a point being in maximo 

 2 km. per second, as determined from earlier investigations, 

 the maximum displacement to be determined is o"o3o 

 Angstrom Unit. In order to get accurate measurements of such 

 small wave-length differences a large dispersion is necessary. 

 On the Cambridge plates this amounted to i mm. pero-88 A.U. 

 The measurements were all carried out by Mr. N. Tunstall, 

 student uf Manchester University, by means of the spectro- 

 comparator shown. 



A total of 194 plates had been taken and measured. 

 'J'he plates, which were all obtained within one fortnight in 

 June, 191 1, gave comparisons between points situated, not, 

 as in the earlier investigations, at the ends of solar diameters, 

 but between points at 90° apart all round the sun. For 

 each complete set of observations round the sun, of which 

 there were four in all, it was possible to obtain two in- 

 dependent determinations of a quantity E representing the 

 difference between the sum total of ten velocities at certain 

 latitudes in the Northern and the sum total of ten velocities at 

 the same latitudes in the Southern hemisphere of the sun. Of 

 this difference, which in case of symmetry round the solar 



