1842.] of the Himmalay a Mountains. v 



used when they fell in the line, and they have not unfrequently been 

 found of value as terms of comparison by which to judge of the ac- 

 curacy of the barometrical results. 



[The nomenclature adopted, is that of MacCulloch' s~\ Hebrides. It were 

 no doubt very much to be desired, that a system of nomenclature found- 

 ed altogether on mineralogical distinctions, (like Brogniart's for instance,) 

 should be generally received by geologists. It would save much useless 

 and cumbrous description. Till such a reform, however, be introduced, 

 the safest plan is to follow the example given in the above work, of 

 noticing and describing correctly every compound included under any 

 general head or term, as constituting a distinct geological formation. 

 By this means the danger of confusion is entirely obviated. 



Silt, sand, gravel, or boulder stones which are evidently derived from 

 the breaking up of pre-existing rocks, and are of the latest formation, 

 are all comprehended by Dr. MacCulloch, under the term " alluvium of 

 transport." Professor Buckland was, I believe, the first to establish in a 

 satisfactory manner, that there are deposits which may be discriminated 

 as originating in two distinct causes, either in the action of the present 

 rivers of the globe, or of a mighty rush of waters or deluge, far surpass- 

 ing the greatest effect of rivers as they exist at present even in their 

 highest floods. To the former, the term alluvium is restricted. The 

 [latter he distinguishes by the term diluvium, and though this cause may 

 not have operated on every occasion, yet it is always useful to] bear it in 

 mind. Its reality in some particular cases is too obvious, at least in 

 this quarter, to escape the notice of the most indifferent, or even pre- 

 judiced observer. I have therefore adopted these terms, considering 

 them conducive to precision, and as having the sanction of such high 

 authority. The angular fragments and rubbish, which are general- 

 ly found either in their original position or only so far removed as 

 may be traced to the action of gravity, are termed by Dr. MacCulloch, 

 " alluvium in situ," and " alluvium of descent." 1 have ventured to use 

 the term debris. 



9. In the mineralogical details, I have adopted the nomenclature late- 

 ly proposed in the system of Professor Mohs of Freyberg. The syno- 

 nyms in this science have, it must be confessed, become too numerous, 

 and the knowledge of them forms a very considerable part of the little 

 that is to be learned from what are called systems of Mineralogy. To 



