BISECTIONS FOE COLLECTING FOSSILS. 4G9 



ponent ingredients, their colour, c. Also the texture, such 

 as the crystalline-granular, the slaty, the compact, &c., are 

 subject to variation, and gradual changes have often taken 

 place through atmospheric influence, sometimes to a con- 

 siderable depth into the mass. Accidental admixtures, not 

 essential to the rock, are likewise frequently observable. As 

 in such cases a few specimens would convey but an imperfect 

 idea of the true character of the stratum, or other mass of 

 rocks, suites of specimens should be formed, illustrative of 

 most of the varieties which it affords. 



5. The thickness of each stratum or bed, and other 

 circumstances connected with them, such as their horizon- 

 tality or inclination, and the angle under which, and toward 

 what part of the compass they incline, should be regularly 

 noted. Slight sketches of the stratification of a coast or 

 cliff, marked with numbers corresponding to those on the 

 labels of the specimens obtained from those strata, will be 

 found greatly to abbreviate the trouble of writing descrip- 

 tions on the spot. 



6. Examine all places where coal-pits are sunk through 

 different strata ; procure specimens from these, and likewise 

 of the different varieties of coal, paying particular attention 

 to specimens of vegetable impressions which they, or any of 

 the accompanying rocks, such as sandstone, &c., may afford. 



7. JSTo opportunity should be neglected to procure 

 secondary fossils of every description, accompanied by 

 specimens of the masses in which they are imbedded, and 

 which are not seldom chiefly characterised by them. Interest 

 should, therefore, everywhere be made with quarry-men, and 

 persons engaged in all sorts of works of excavation, to pre- 

 serve whatever may be found by them in the way of petri- 

 factions, especially osseous remains ; and those persons 

 should be particularly cautioned against breaking to pieces 

 whole skeletons, or large portions of them. If possible, the 

 collector should in person superintend the excavation. The 

 following suggestions, taken from Sir H. De la Beche's 

 excellent treatise, " How to observe in Geology," particu- 

 larly apply to osseous remains of an extremely delicate 

 structure. Instead of endeavouring to extract these on the 

 spot, the observer should detach so much of the rock as shall, 

 to the best of his judgment, envelope the organic remain in 



