1878.] 



115 



[Lesley. 



that any lack of homogeneousness in any bed might be detected by analy- 

 ses of two specimens taken from places in the edge of the bed from 5 to 

 30 feet apart, according to the depth of the cut, and sometimes by the se- 

 lection of a third and intermediate specimen, many of tbe analyses of indi- 

 vidual specimens being also repeated. 



The investigation was continued throughout the winter by Mr. Hen ly 

 Hartshorne, and completed during the summer by Mr. Hartranft ; and I 

 now find myself able to bring some ot the results to the notice of the Society 

 in the form of tables, (1) of analyses, and (2) of averages. At a future 

 time I will be able to carry the discussion of averages still further, and 

 can then venture to base upon them some hypothetical conclusions of great 

 interest to geologists who occupy themselves with the problem of the 

 genesis of our limestone deposits. 



Table I, gives the whole series of analyses made ; but includes only the 

 determinations of Carbonate of Lime, Carbonate of Magnesia, and Insolu- 

 ble Matter ; omitting the determinations of oxide of iron, alumina, sul- 

 phur, phosphorus and carbon. 



This table shows to the eye, without need of a diagram, the remarkable 

 alternations of limestone beds with dolomitoid beds throughout the series. 



Table I. 



Analyses of specimens taken from railroad cuttings opposite Harrisburg ; 

 in two series : one at railroad grade ; the other near the top of the cut. 



Note, when the analysis was repeated, with slight difference, the average is 

 given ; but the instances of this are few. 



