102 PROCEEDINGS OF THE AMERICAN ACADEMY 



exclude the possibility of other light mixed up with the polarized 

 light, though itself unpolarized, and which is generated on the spot by 

 changes which take place in the comet, making it to a certain extent 

 self-luminous. The great comet of 1843, the next comer bright enough 

 to allow of an examination into the nature of its light, was too brief a 

 visitor, and too unfavorably situated when seen, to allow of any such 

 observations, at least upon its nucleus. But the bi'iUiant comet of 

 1858, which now distinguishes by its presence the northern sky, has 

 lingered so long in view as to invite a renewed study into the origin 

 of cometary light. By the invitation of Mr. G. P. Bond, I have twice 

 visited the Observatory of Harvard College, and examined the light of 

 this brilliant comet, when condensed in the focus of the great equatorial 

 refractor. On the first of these occasions a Nicol's prism was used, and 

 the changes in the brightness of the image cori'esponding to the rota- 

 tion of the analyzer were very decided ; and the positions of maxima 

 and minima were indicated with complete unanimity in many inde- 

 pendent experiments by Mr. Bond and myself. These experiments 

 were made in such a way as to guard against self-delusion, — the 

 experimenter not being able to see the position of his analyzer while 

 he was judging of its positions of maxima and minima transmission of 

 the light. On the second occasion, Savart's polariscope was used, in 

 which plates of quartz and tourmaline are so combined as, with polar- 

 ized light, to give colored fringes. The first glance through the polari- 

 scope at the light of the comet, condensed in the focus of the telescope, 

 showed the field of view traversed by colored fringes, and betrayed 

 strong traces of polarization in the light of this comet. If it is per- 

 mitted to generalize from the few comets, on which experiments have 

 been made, to comets in general, there can be no doubt that the comets, 

 notwithstanding the almost universal absence of phase, are indebted to 

 the sun for most, if not for all, of their light." 



Dr. J. B. S. Jackson exhibited some specimens of the so- 

 called Rocky Momitain Corn, in which each kernel has its 

 own investing husk ; this he had raised himself, and he no- 

 ticed that some ears of common naked corn grew from the 

 same seed. This has been supposed to be the original state 

 of Indian Corn. 



Professor Gray remarked that there is no evidence, and no 



