1890.] NATURAL SCIENCES OK rHILADELPIIIA. 479 



aniiiiatioii of the ])hysiographical and biological features of some of 

 tiie most gigantic volcanic summits on the surface of the earth. 

 The four highest mountains of the Republic were asce;ided by two 

 or more members of the party within the limited period of three 

 weeks, and thus a good opportunity was afforded for testing relative 

 (altitude) values by means of the barometer. The order of the 

 ascents was as follows : The peak of Orizaba, 6th and 7th of April ; 

 Popocatepetl, 16th and 17th of the same month; Nevado de Tolu- 

 ca, on the 21st, and Ixtaccihuatl, on the 26th and 27th. The de- 

 terminations of altitude have been recorded in a paper published 

 in the October issue of the Proceedings of the Academy. 



Some little exploration was made of the lake and valley region 

 of the capital city ; but the most important work was accomplished 

 along the eastern and southern face of the central plateau, or in the 

 great contour comprised between Jalapa and the volcano of Jorul- 

 lo, on the Pacific slope. The edge of the plateau was crossed and 

 recrossed at several points, and it was thus possible to fix definitely 

 the structural relations of one of the most remarkable orographic 

 features on the American continent. The quarries of the famous 

 Mexican onyx, lying in the mountain fastnesses southwest of Te- 

 huacan, were visited, and the geological relations of the peculiar 

 marble ascertained. The ten days immediately j^receding the de- 

 parture from Mexico were devoted to a zoological reconnoissance of 

 the ocean-front about Vera Cruz, and to the exploration of the 

 outlying coral reefs. 



It is not yet possible to recite fully the scientific results of the 

 Academy's expedition, inasmuch as a considerable part of the material 

 and data obtained by it still awaits study and examination. But it 

 is certain that they have fully met the expectations of the principal 

 promoters of the enterprise, even if it cannot be said that the 

 success was equal in all the special departments which the expedi- 

 tion attempted to cover. Among the more important results ob- 

 tained may now be mentioned : 



1. The determination of the geological features of Yucatan. 



2. The discovery (at least to science) of the existence of extensive 

 coral reefs in the western waters of the Gulf of Mexico. 



3. The determination of the culminating point of the Mexican 

 Republic, which is also the culminating point of the North Ameri- 

 can Continent. 



