COAL MINES OF EASTERN VIRGINIA. 533 



plants, and in some localities with those of fish, rest directly upon 

 the principal mass of coal, and occupy the interval between 

 the seams, where there are two. 



The most common dip is towards the west, often at a very 

 high angle, but owing to original irregularities in the gneissoid 

 floor, and enormous dislocations subsequent to the filling up of 

 the basin, the strike and inclination of the beds are subject to 

 sudden and great transitions. 



The open texture, high inclination, and fractured condition of 

 the strata, favoring the descent of streams from above, cause a 

 large influx of water into many of the worldngs. This forming 

 part of the liquid collected in the wells at the bottom of the prin- 

 cipal shafts, prior to its removal by the buckets, imparts as I have 

 always found, a lower temperature to the mass of water there 

 accumulated than is proper to the bottom strata. The small 

 streams flowing from between the surface of the granite and the 

 coal, or from the rocks above the coal, have, on the contrary, 

 always presented a close approximation to the temperature of the 

 strata from which they make their escape. I have therefore, 

 whenever practicable, resorted to such streams, occasionally com- 

 paring their temperature with that of the adjoining rocks, by a 

 thermometer, duly inserted in the mass. 



Some of the following observations, it will be seen, were made 

 in workings in active operation, and where the heating effects of 

 the workmen, mules, and lamps, might be supposed to have made 

 the results too high. The amount of their influence, however, 

 could not have been considerable, as the temperature was deter- 

 mined by plunging the thermometer into a body of water con- 

 tinually replenished from the rock. Indeed, as will be proved in 

 the sequel, this influence upon the average result was more tha)r 

 compensated by the cooling effect of the drippings from above. 



The remaining observations were made in shafts just com- 

 pleted or in progress, and where the chief modifying influence 

 was the cooling agency of the drippings from the higher beds. 



