532 SUBTERRANEAN TEMPERATURE IN THE 



Observations of Subterranean Temperature in the Coal- 

 MiNEs OF Eastern Virginia. By Wm. B. Rogers, Professor 

 of Natural Philosophy in the. University of Virginia. 



The important law of an augmenting temperature as we de- 

 scend to considerable depths beneath the surface of the earth, 

 has, it is well known, been amply demonstrated in regard to 

 Europe, by the numerous observations made in the mines and 

 artesian wells of that portion of the globe, but with the single 

 exception of Humboldt's observations in Mexico, no direct re- 

 corded proof has yet been furnished of its applicability to the 

 Continent of America. The results detailed in the present com- 

 munication, forming the first published confirmation of this law 

 as regards any part of the United States will, therefore, it is con- 

 ceived, be viewed as an important contribution to our knowledge 

 on the subject, and will, it is hoped, conduce to more extended 

 observations of the same description in other parts of our country, 

 where the requisite opportunities exist. 



The mines in which these results have been obtained, lie in 

 the most productive part of the Oolite coal-measures of Eastern 

 Virginia, and are of various depths, from 100 to nearly 800 feet. 

 These coal-bearing strata rest upon an irregular basin-shaped 

 floor of sienitic and gneissoid rocks, which forms the lower limit 

 of the workings, and is penetjated for a few feet by some of the 

 deeper shafts, as well as by the shallow ones nearest the margin 

 of the field. They consist in great part of felspathic and mica- 

 ceous sandstone, the coarser beds of which, formed of the almost 

 unworn materials of the neighboring crystalline rocks compactly 

 reunited, are sometimes scarcely distinguishable from the wea- 

 thered portions of the parent mass. 



The coal, consisting of a single seam, or of two contiguous 

 seams, having an aggregate thickness varying from twenty to 

 fifty feet, lies within a few feet and sometimes a few inches of 

 the undulating floor, separated from it by bituminous slates and 

 shales. Beds of the latter material, abounding in impressions of 



