242 ROLLIN T. CHAMBERLIN 



To determine their average vertical dimension, the cross-sections 

 were photographed and the glazed-paper prints carefully cut at the 

 railroad-level as base-line, and the top of the Pottsville conglomerate 

 as the sky-line, and the resulting paper equivalents of the sections 

 then weighed on delicate balances. At the same time similar strips 

 of duplicate prints, cut to represent a uniform height of one mile of 

 strata above the base-line, were also weighed. Thus weighed in the 

 five separate sections, the results were: 



Grams 



Section i weighed 0.4819 



Scale representing same area weighed, per mile of height. . o. 1394 

 Hence average height of reconstructed beds of Section i 

 is 0.4819/0. 1394=3.45 miles. 



Section 2 weighed o . 4346 



Scale representing strata uniformly i mile thick for this 



distance weighed o . 1833 



Hence average height of reconstructed beds of Section 2 is 



0.4346/0.1833 = 2.37 miles. 



Section 3 weighed 0.4231 



Scale representing i mile of strata over this area weighed. . o. 1466 

 Hence average height of reconstructed beds of Section 3 is 

 0.4231/0. 1466=2.88 miles. 



Section 4 weighed o . 3981 



Scale for this distance weighed o . 1466 



Hence average height of reconstructed beds of Section 4 is 

 0.3981/0.1466=2.71 miles. 



Section 5 weighed o . 5402 



Scale for this distance weighed o . 1466 



Hence average height of reconstructed beds of Section 5 is 

 0.5402/0.1466=3.68 miles. 



The general average height of the strata over the last four sections 

 can be obtained directly by dividing the sum of the weights of the 

 four paper sections by the total weight per mile of elevation of the 

 corresponding scales. 



Grams 



Total weight of Sections 2, 3, 4, and 5 i . 7960 



Total weight of corresponding unit mile scales o . 6231 



Average height for these sections, 2 . 88 miles. 



Section i cannot be averaged in thus, as it was photographed on a 

 slightly different scale. But the length of Section i on the original 



