GEOLOGICAL AND NATUUAL HISTOIIY SUKVEYS. 455 



map embraces the South Mountains of Berks, Lehigh, and North- 

 ampton counties from the Schuylkill to i\m Delaware, and includes 

 the border of the Trias on the south, and the limestone region of the 

 great valley on the north, with all its iron ore mines. The third, 

 partly published and nearly finished, covers the South Mountain 

 region from Harrisburg to the Mnrylaiid line: ))Vit its geology is 

 still to be worked out. 



Numerous local maps oT the same character, instrumentaiiy sur- 

 veyed, in various parts of the State, will contribute their quota to 

 a future complete relief map of the State. An iiiiportant and 

 largo addition of these data has been made by the water depart- 

 ment of Philadelphia, under Colonel Ludlow. It is an extension 

 of the survey map of the South Mountains, southward o^er the 

 Tri;us region of Bucks and Montgomery, toAvard Philadelphia. With 

 this map in hand the survey can now work out the geology of the 

 N'ew Ked Belt between the vSclmylkill and Delaware Eivers, in 

 a tolerably satisfactory manner. But the whole belt must be thus 

 mapped before some of the paradoxical exhibitions of this inter- 

 esting formation can be thoroughly well understood. 



As for the azoic belt of the southeastern corner of the State, from 

 Trenton, past Philadelphia and We^t Chester into Maryland, espe- 

 cially that part of it west of the Schuylkill, it seems hopeless to un- 

 ravel its structure before a complete and accurate relief of the sur- 

 vey, in the minutest detail, has been obtained. No general sui'vey 

 of it avails. Several years of hard work has been expended upon it, 

 but the geology remains as obscure as ever. Two local relief maps 

 only have been made, which reveal important facts, and show what 

 may be expected from this kind of work wherever it shall be faith- 

 fully done. But the Philadelphia azoic belt wdll continue to be th(i 

 pG7hs osinoruin of Pennsylvania geology for yeai*s to come. Ap- 

 palachian geology is child's play compared with it. 



All field work of the second survey closed with June 1, 1890, after 

 which date work was continued for the completion of its publica- 

 tions, chiefly the last sheets of the anthracite survey, the maps and 

 sections of the survey of the n(>w i-ed belt of Bucks and Montgomery 

 counties, the completion of the bituminous colliery, map of western 

 Pennsylvania, a new geological State maj),' and the three volumes 

 of the final report. Of the latter, volumes 1 and 2 were prepared in 

 person by Lesley, and some 200 pages of part 1 of volume 3. Fail- 

 ing health compelled him to relinquish the work at this point, and it 

 was (completed by E. V. d'Invilliers and A. D. W. Smith. Volumes 

 I and 2 appeared in 1892 and vohune 3 in 189.'>. They comprise 

 2,638 octavo pages of text and Oil plates. 



' X'ol. ] of Final Reports, Geological Survey of Pennsylvania, 1892, p. 3. 



