472 APPENDIX. 



those of disintegration and of partial transportation, 

 that we shall obtain descriptions not hitherto given; 

 while if, under the fluviatile alluvia, the several effects 

 in changing the original surface especially demand at- 

 tention, so, in describing the maritime ones, not only 

 should the changes of the coasts be noted, but the 

 soundings of the neighbouring seas and the alterations 

 which the relative level of the sea and land appear to 

 have undergone. In connection with this, should also 

 be described the deposits of peat, with their associated 

 marls, together with the organic fossils of the alluvial 

 soils: while I may here say, once for all, that these 

 will demand attention in every subsequent description 

 of the strata, under all the circumstances of their na- 

 ture, positions, &c. which may throw any light on a 

 subject often obscure. In describing the rocks of a 

 district, it is generally convenient to commence with 

 the lowest, as, with granite, if present; thus ascending 

 through the strata, and terminating with the trap rocks, 

 or, if they exist, with tertiary deposits and volcanoes. 

 Yet it is often convenient to proceed in the reverse 

 order : while, if no absolute rule can be given, the object 

 is to gain some fixed point of departure to which every 

 thing can be referred, that the reader may acquire cor- 

 rect ideas, not of the names alone, and geographical 

 places of rocks, but of all their relations. The endless 

 volumes of useless description, compel me to caution 

 the geologist against imagining that he has described a 

 district by the mere enumeration of its rocks; often 

 even careless whether they are not transported and 

 foreign substances. 



In granite, the extent and position of the masses should 

 first be noticed; with any rational inferences respect- 

 ing what is invisible. To this must be added its dis- 

 position, with its concretionary or other forms, as also 



