5. One of the most advantageous situations for obtaining specimens, and examining the relations of rocks, is in the sections afforded by cliffs on the seashore; especially after recent falls of large masses. It commonly happens that the beds thus exposed are more or less inclined; and in this case, if any of them be inaccessible at a particular point, the decline of the strata will frequently enable the collector to supply himself with the specimens he wishes for, within a short distance. Thus, in Sketch 4, which may be supposed to represent a cliff of considerable height, the observer being situated at a, the beds b, c, d, though inaccessible at that place, may be examined with ease and security, where they successively come down to the shore, at b prime, c prime, and d prime.
6. To examine the interior of an unknown country, more skill and practice are required: the rocks being generally concealed by the soil, accumulations of sand, gravel, etc., and by the vegetation of the surface. But the strata are commonly disclosed in the sides of ravines, in the beds of rivers and mountain-streams; and these, especially where they cross the direction of the strata, and be made, by careful examination, to afford instructive sections.
7. Among the distinctive circumstances of the strata, the remains of organized bodies, shells, corals, and other zoophytes, the bones and teeth of animals, fossil wood, and the impressions of vegetable stems, roots, or leaves, etc., are of the greatest importance; affording generally the most marked characters of the strata in which they occur. These should, therefore, be particularly sought after, and their relative abundance or rarity in different situations noticed. The petrified bodies should, if possible, be kept united with portions of the rock or matrix in which they are found; and where they are numerous, in sand, clay, or any moist or friable matrix, it is in general better to retain a large portion of the whole mass, to be examined afterwards, than to attempt their separation at the time of collecting.
8. The loose materials which are found above the solid rocks, in the form of gravel, silt, rolled pebbles, etc., should be carefully distinguished from the solid strata upon which they repose. And the more ancient of these loose materials, found on the sides or summits of hills, etc., should be distinguished from the recent mud, sand, and gravel, brought down by land-floods, or rivers. The bones and teeth of animals are not unfrequently found in gravel of the former description; and the collection of these remains from distant quarters of the globe, is an object of the greatest interest to geology.
9. Besides a note of the locality, there ought, if possible, to accompany every specimen, a short notice of its geological circumstances; as:
Whether it be found in large shapeless masses, or in strata?
If in strata, what are the thickness, inclination to the horizon, and direction with respect to the compass, of the beds? [If these cannot be measured, an estimate should always be recorded, while the objects are in view.] Are they uniform in dip and direction? curved, or contorted? continuous, or interrupted by fissures or veins?