194 PROCEEDINGS OF THE ACADEMY OF 



baad is caused by the absorption of the other constituents of white light in 

 traversing so great an amount of atmosphere. This hypothesis is also main- 

 tained by Mr. Martin in his Notes, F. p. 497 : and he gives a much fuller and 

 better account of the phenomenon as observed in morning twilight by M. 

 Bravais from the summit of the Faulhorn. If it were really due to this cause. 

 no reason could be assigned for the gradual fading and disappearance, first of 

 the yellow and then of the red light, when they have risen about 20° above the 

 horizon ; they ought to follow the sun completely across the sky. I believe 

 the phenomenon to be due to the formation of an iris by the sun's light 

 falling on the vapor of the atmosphere which has become partially con- 

 densed as the sun has receded ; probably this will be found to correspond 

 with the iris given by five internal reflections and two refractions of the 

 sun's rays. 



November 11th, 1857. 

 Vice President Lea in the Chair. 



The following papers were presented for publication in the Proceed- 

 ings : 



'■' Descriptions of some new Reptiles collected by the U. S. Exploring 

 Expedition, under the command of Capt. Chas. Wilkes, U. S. N., by 

 Charles Girard." 



" Notices of new Genera and species of marine and fresh-water fishes 

 from Western North America, by Charles Girard." 



•• Description of a new species of Cypselas, collected in the N. W. 

 Boundary Survey, A. Campbell, Esq., Commissioner, by C. B. R. Ken- 

 nerly, Surgeon and Naturalist of the Expedition." 



" Notes on the American species of Archibuteo and Lanius, and 

 Description of a new species of Toucan, of the genus Selenidera, by 

 John Cassin." 



Which were severally referred to Committees. 



Mr. Cassia read the following extract from a letter of Mr. P. B. 

 DuChaillu. 



Fernando Paz River, August 11 Ih, 1857. 



" While hunting after the Gorilla a few days ago, I met with a male surrounded 

 by a few females. The male has a red crest, like a cock. 



"Both the guinea fowl and the black pheasant are birds which are not seen 

 before you reach fifty or sixty nailes in the interior, and are unknown to the 

 natives of the sea shore. The birds of the Fernando I'az country, until you 

 reach the interior, are exactly the same as those of Cape Lopez, the country 

 being similar in appearance. At the Cape properly there is no town : the largest 

 town of the Cape Lopez people is Sangatonga, situated in the bay formed by 

 the Cape. It is the residence of the king, and is situated in a beautiful prairie 

 at the foot of a hill rising about two miles in the interior. The soil of Cape 

 Lopez is generally light and sandy ; the country presents an aspect quite dif- 

 ferent from that between Fernando F6 and the Gaboon, looking a good deal 

 like the countries of Southern Africa toward the Cape of Good Hope — large 

 prairies with groves of trees. In these groves the Cape Lopez people have their 

 plantations, as the soil is good. Sweet potatoes, cassada, plantain, ground nuts 

 and sugar cane are the products. They plant in pretty large quantities, as these 

 form the main staple of their food; sweet potatoes, especially, grow well. Good 

 roads could easily be made, and would be a powerful aid to colonization. The 

 raising of cattle could be made a profitable business, for the prairie land would 

 afford good grazing. A good many wild cattle are seen wandering over the 



[November, 



