288 T. O. MABRY 



reached the Lignitic beds at a depth of about 180 feet. Wells 

 in Oxford struck the same beds at depths of 155 to 160 feet. 



The pipe clay of which these bowlders are composed is also 

 of an unctuous, kaolinic nature, such as would not seem able to 

 suffer prolonged transportation by running water without disin- 

 tegration. 



3. The clays of this bowlder stratum are altogether unlike 

 those of the Lignitic beds near here, which are generally blue, 

 or black, pyritiferous, and friable when dry. But the clays, also, 

 of the Lafayette proper, which must have come from a distance, 

 show a like dissimilarity to the Lignitic clays, having become 

 altered probably in color and relieved largely of carbonaceous 

 matter and of iron pyrites (if they came from the Lignitic) dur- 

 ing transportation or subsequent to their redeposition. So the 

 argument based on the dissimilarity of the clay bowlders to 

 clays of pre-Lafayette age in this vicinity is of no value consid- 

 ered apart from the conditions under which they must have been 

 deposited, and the short distance to which they could have been 

 transported by running water. 



4. These bowlders are frequently highly fossiliferous, con- 

 taining plant specimens preserved in ferric oxide, and prolonged 

 water transportation, if possible, would probably have defossil- 

 ized them by the removal of the iron oxide in solution. The 

 fact that no well-defined fossils peculiar to itself have yet been 

 found in the Lafayette might be adduced as evidence that these 

 fossiliferous bowlders must have come from some other source 

 (and the character of the fossils as described by Dr. Knowlton 

 would seem possibly to indicate their derivation from an earlier 

 formation) ; but this does not necessarily follow, since plants must 

 have existed during the Lafayette, and if none have been found 

 in it the explanation is probably to be found in the fact that its 

 materials, as a rule, are not well adapted to the preservation of 

 organic remains. Its clays, moreover, as already pointed out, 

 are very similar to those of the stratum under discussion, and 

 the latter are very rarely fossiliferous. It is only occasionally 

 that we find fossils in compact, close- textured, impermeable and 



