110 PROCEEDINGS OF THE BALTIMORE MEETING 



As to quality, the peculiar features of Mexican petroleum lie in the relatively 

 low percentage of light distillates and the relatively high sulphur content. It 

 furnishes little gasoline in comparison with its bulk, and this percentage has 

 not been raised to a high figure through cracking processes. However, Mexico 

 offers an immense reserve of fuel oil, though for fuel much of the oil needs an 

 admixture of more fluid oil, or special burners adapted to its high viscosity. 

 Its percentage of undesirable sulphur is reduced most readily by the addition 

 of sulphur-free oil. 



The accessibility depends on many considerations, including its distance from 

 the points where it is refined and used and from the sources of labor and sup- 

 plies, on the tankers, pipe-lines and other transportation facilities available, 

 and on political conditions in and around the fields arising out of local disturb- 

 ances, and the decrees issued by the Mexican Government involving high taxa- 

 tion (15 to 20 per cent), and nationalization or threatened "confiscation of 

 private property and arbitrary deprivation of vested rights." If sufficient 

 tankers had been available, the production for 1918 would have been five or 

 ten times greater. 



Presented by title in the absence of the author. 



AMEBIC AX MAPPING IN FRANCE 

 BY GLENN S. SMITH ^ 



Presented in abstract from notes. 



THE AMERICAN TOPOGRAPHER IN THE ROLE OF ARTILLERY ORIENTATION 



OFFICER 



BY F. E. MATTHES 



Presented in full extemporaneously. 



Discussed by Messrs. Glenn S. Smith, J. Eussell Smith, H. F. Reid, 

 G. 0. Smith, and W. M. Davis. 



President Cross, of the Geological Society of America, resumed the 

 chair, the joint session dissolved, the members of the Association of 

 American Geographers retiring to continue their own program in their 

 usual meeting place, and the Geological Society of America took up its 

 special papers again, as follows : 



A METHOD OF AERIAL TOPOGRAPHIC MAPPING 

 BY FRED H. MOFFIT AND J. W. BAGLEY 



Read in full from manuscript by the junior author. 



In the discussion, Dr. R. B. Marshall, cf the United States Geological 

 Survey, gave some concrete examples of the accurate mapping which had 

 been done by Messrs. Bagley and Moffit with their aeroplane camera. 



1 Introduced by N. M. Fenneraan. 



