1876.] ^■*- [Lesley. 



Contributions to the Phjsical Geography of the United State s^ 

 hy Charles Allen^ Assistant in charge of the Collection and 

 Collation of Railroad and other Levels for the Second Geolog- 

 ical Survey of Pennsylvania. 



By J. P. Lesley. 



(Read before the American PMlosopMcal Society, January 15, 1876.) 



In presenting to the attention of the members Mr. Allen's 

 list of Pennsylvania levels, I have only to say that the pro- 

 gress of physical geography in the United States has been so 

 rapid, of late years, as to attract the attention of the Scien- 

 tific world at home and abroad, and that its connection with 

 the progress of geological science is so intimate, that work- 

 ing geologists hail with lively pleasure the publication of all 

 hypsometrical records of a genuine kind, whether old or 

 new. For want of government bureaus of statistics the 

 greater part of such records have been irrecoverably lost. 

 Of the tentative work of our railway, canal, slackwater and 

 turnpike companies, done between 1830 and 1860, scarcely 

 a trace remains ; although, if its records could be recovered 

 and printed, they would furnish copy for hundreds of 

 volumes. Since 1860 the destruction has not been so com- 

 plete, but has been nevertheless very great. There are re- 

 cent important surveys of which no records can be found, 

 even in the offices of the companies for whom they were 

 made. 



This important subject has received well-deserved atten- 

 tion at the hands of the chiefs of the United States Explor- 

 ing Expeditions, who are mapping the interior of the Conti- 

 nent. But some efficient organization is required for the 

 preservation and publication of levels in the States lying 

 between the Atlantic and the Mississippi. 



The State Geologists of Ohio and North Carolina, also, 

 have published valuable hypsometric tables. 



