262 GENERAL GEOLOGY. 



strata; and in Lncas, Warren, and Madison comities, lie finds 

 himself among the strata that bear the thin and usually 

 uprofitable beds of coal of the Middle coal-measnres. Let 

 shafts be first snnk where only these last named beds of coal 

 are fonnd, for it is certain that if the heavier beds of coal which 

 we have seen near the surface farther eastward exist here at 

 all, they cannot lie at any great depth beneath the bottoms of 

 the valleys there. If successful in these trials, go farther np the 

 valleys, and if again successful, cross over the Great Water- 

 shed to the valleys of the western drainage, and finally to the 

 valley of the Missouri river itself. If the plan here suggested 

 should be acted upon, it will be of the utmost importance that 

 the most accurate and careful record should be preserved of 

 the thickness and character of the different strata passed 

 through before the coal was reached. By means of only a 

 few such data, with the character and thickness of each 

 stratum accurately known, a competent engineer would be 

 able to determine, with a good degree of accuracy, the depth 

 at which the same bed of coal might be reached at other 

 points, at least in the same vicinity. 



Let the fact be demonstrated that the beds of coal of profit- 

 able thickness do actually extend beneath the surface to the 

 westward, as they are here assumed to do, careful records 

 being kept of all the strata passed through in digging, and 

 coal-mining in western and southwestern Iowa will, within a 

 few years afterward, be reduced to a system as reliable in its 

 results as that adopted in our eastern or in European mines. 



In this connection, it is of the greatest importance that the 

 fullest possible information should be had concerning the 

 identity of the coal-beds over wide areas, that we may note 

 the changes which take place in their thickness, quality, etc. 

 This can only be done with any degree of certainty, by long- 

 continued observation and patient labor, which is now 

 prevented by the discontinuance of the Survey. Enough, 

 however, has already been learned to show that although the 

 coal-beds may be identified at great distances in some cases, 

 they all lack, to a greater or less extent, a uniformity of 



