WESTERX COAL-FIELDS OF THE OHIO VALLEY. 5 



glomerate for which this could be mistaken. At certain points traces of 

 vegetable impressions may also be fbuntl in these deposits. They are 

 very indistinct, but quite resemble the imj^ressions so common in some 

 parts of the conglomerate series, both in the eastern and the western 

 fields. Associated with this debris, when found along the Muldraugh- 

 hill district, we have a quantity of the waste from the St. Louis lime- 

 stone, tlie uppermost purely calcareous member of our Subcarboniferous 

 limestone series. This association is strongly confirmatory of the idea 

 that this conglomerate is that of the coal period. 



The whole of the Green river basin in the counties of Adair, Green, 

 Metcalfe, and parts of others, has its hill-tops covered by the beds of 

 the A^'arsaw division of the St. Louis group. From this level to the 

 base of the coal-bearing series, where that is left in the region, to the 

 east of this district, is not over one hundred and fifty feet. In the dis- 

 trict to the west, the thickness of the St. Louis is greater, being about 

 two hundred and fifty feet on the average. Above the St. Louis the 

 Chester sandstone, which is the transition series from the deep sea lime- 

 stones below to the land beds above, is perhaps about one hundred feet 

 thick. In its upper part we have some thin coal seams, one of which is 

 about eight inches thick, and is found over an extensive section in the 

 western coal-fields ; so we are safe in asserting that there is only rec[uired 

 to be restored to this district of the upper Green river a total thickness 

 of from two hundred to two hundred and fifty feet to return the car- 

 boniferous horizon to it. Is it likely that this thickness of deposits has 

 disappeared from this region? It seems to me that we are forced to giA'e 

 an affirmative answer to this question. It needs but a glance at the con- 

 ditioiLs of this district to make it clear that it is wearing down with great 

 rapidity compared Avith other parts of the Mississippi Valley. We know, 

 from the labors of Humphreys and Abbott, that the erosion of the Mis- 

 sissippi Valley is now going on at the rate of one foot in seven thousand 

 years. As this erosion is in the main proportionate to the amount of 

 rainfall, it is doubtless about twice as great in this section of the Ohio 

 Valley as it is over the whole ^Mississippi drainage system. I am sat- 

 isfied that one foot in three thousand five hundred years is not too much 

 to allow for the ablation of the surfiice of this region. At this rate the 

 destruction of the three hundred feet of beds which I believe have been 

 wasted from this district between the coal-fields since the conglomerate 



