242 P''of- Sedgivick oji the Origin [April, 



account, or to draw a single just conclusion from them. This 

 censure does not, however, apply equally to them all. A writer 

 inth^ two last numbers of the Edinburgh Philosophical Journal 

 c&Rsiders the present classification of the superficial detritus of 

 the earth to be founded on an imperfect induction, and to be 

 contradicted, or at least invalidated, by the distribution of the 

 organic remains contained in it. Though I am opposed to many 

 of the conclusions of this author, and think that he has been 

 misled from a want of a more extended knowledge of the pheno- 

 mena in question, yet I willingly allow that his arguments are 

 adduced with a sincere love of truth, and that his facts and 

 inferences are entitled to a candid examination. It is not, how- 

 ever, my intention formally to enter the field of controversy. 

 Prof. Buckland is far too secure in his position, and incompa- 

 rably too well armed to need any such assistance. 



The words alluvial and diluvial detritus designate certain 

 classes of phenomena which at the same time have a distinct 

 character, and belong to distinct epochs. The propriety of this 

 assumption can only be made out by direct observation. If it 

 appear that alluvial formations commonly rest on diluvial ; that 

 the converse is never true ; and that the two formations never 

 alternate : then the distinction just alluded to is completely made 

 out, and rests on exactly the same evidence as the order of 

 superposition of any known strata. We may further observe 

 that this conclusion is quite independent of any zoological 

 arrangements. When the order of superposition has been once 

 made out, we may then proteed to examine the zoological pheno- 

 mena of each successive deposit. Before that time, organic 

 remains, however interesting in themselves, convey little inform- 

 ation respecting the revolutions to which the earth's surface has 

 been subjected. It has been already observed that the words 

 diluvial detritus were applied to certain materials brought into 

 their present situation by great irregular inundations. In what 

 sense all diluvial formations may be considered contemporane- 

 ous ; to what extent, and in what manner, diluvial torrents have 

 acted on the earth's surface, are simply questions of fact to be 

 determined by physical evidence, and by physical evidence 

 alone. 



The truth of any physical phenomenon can only be made out 

 by physical evidence, and no appeal ought to be made to any 

 other authority before that evidence has been completely inves- 

 tigated. It is then obvious that every conclusion respecting the 

 classification of formations, of whatever age, can only rest on the 

 evidence aftbrded by direct observations. For this reason, I 

 have drawn up, for insertion in t\\e Annals of Philosoplnj, an 

 account of some of the alluvial and diluvial deposits which I 

 have had an opportunity of personally examining. Part of the 

 succeeding statements may be considered vmnecessary, and 



