. III. DIST. CHAR. Soil. 173 



Obs. The reliquia lodged in veins and fissures, 

 for the most part differ from those which are in- 

 closed in the surrounding rock f, and are generally 

 of a more recent formation ff. 



the slip has been made, is often too narrow or close to admit the 

 materials, with which the opening would otherwise, in all probabi- 

 lity, have been filled, and thus have constituted a vein. 



Pipe veins are openings in the strata of a determinate circum- 

 ference, but indefinitely extended in depth. Pipe veins, we be- 

 lieve, are confined wholly to stratified soils. They have generally 

 somewhat of an irregularly tubular form ; but in structure and 

 dimensions are found to vary considerably, even in the continua- 

 tion of the same vein. Their position is, also, very various : they 

 sometimes pierce through the strata in nearly a perpendicular, but 

 oftener in a sloping direction ; and not unfrequently are parallel 

 with the beds in which they are found. 



t In the faults and troubles of coal soils, we have known 

 marine remains to occur, wliile the intersected strata exhibited 

 only vegetal petrefactions and in the mineral veins of the lime- 

 stone tracts in Derbyshire, wood and other parts of trees are 

 found at the greatest depths, though the rock itself holds only 

 shells and other vestiges of the ocean. 



ft Hence the distinction between extraneous fossils incorpo- 

 rated in the substance of the stratum, c. and those merely 

 lodged in its veins and fissures, must always be carefully attended 

 to. The originals of the first kind were undoubtedly contempo- 

 rary with the formation of the including rock itself, of which they 

 form, as it were, a constituent part; while the extraneous fossils 

 of its veins, in most cases, owe their form to animals or vegetables 

 posteriorly introduced from the surface, by various and often re- 

 cent operations of nature. We must not here be understood to 

 assert, however, that the reliquia of veins, aad those of the sur- 



