120 



Bituminization of Wood. 



quartz pebbles, which bear the marks of shells, encrinites, favos- 

 ites, asterias, &c. ; and there are often associated with it, lumps 

 or sometimes large masses of soft and bright red clay, without 

 grit, of the kind usually found accompanying veins of lead ore, 

 in the western country ; thickness 10 feet. 



Figure 2. 



12 ft. 



No. 3. A bed of bluish clay intermixed with a little sand, 22 ft. 



No. 4. A very thin layer of vegetable matter, consisting of 

 small sticks, some of which are flattened and bitumanized. This 

 bed sometimes vanishes and re-appears at short intervals. Its 

 thickness though varying, may be set down at one inch. 



No. 5. A bed of fine-grained aluminous clay, of a deep blue 

 color, which seems to have a tendency to break into blocks of ir- 

 regular cubic or prismatic forms, on account of thin septse or lam- 

 inae of a ferruginous brown color, which traverse it in various di- 

 rections. Reniform concretions are also formed in this clay, 

 which, when they first fall out, have the color of the clay, and 

 seem to differ from it only by being a little harder. After being 

 exposed for some time, they present the appearance of being 

 worn by running water; their surface becomes of a deep brown 

 color, but if broken, they will be found as light colored within, 

 as the clay in which they originated ; if exposed long enough, 

 the brown color pervades every portion of them. These chan- 

 ges no doubt depends on the decomposition of some compound 



