AGUICUrTURAL MUSEUM 28$ 



thchreJxing up, avcViii'id the whole valleys under wa- 

 ter. ;Vt these periods wht!!i the ocean bathed the foot 

 of' tile mountain!^, of wiich there are every where ma- 

 nifest traces, the higher raountahin, as yet undiniinisbvd 

 hy the los^ of those pwrticles of wliich time and the tor- 

 rents have since despoiled them, augmented the motion 

 and force of the descendinj^j %=, uten, bj' the heiojit and ab- 

 ruptness of their poir.ts. I'heir sunsmits being colder^ 

 were covered with deeper snov s for a !on.<]^er time, and 

 when tbc heats ©f summer, shorter no doubt Imt not less 

 int'-nse than at present, dissolved these snows, the tor- 

 rents, thus formed involved a greater quantity of earthy 

 hollowed out deeper chajmeis. and bore away trees \Aith 

 their roots, and lart^e masses of soil connected with their 

 fibres, all which ihey deposited m tlJe lowest shelves of the 

 mountains. In followinsf years new w.ecks accumulate 

 and cloy the ancient ehanncis : the torre;:ts impeded thus 

 by mounds of their own creating, have their voicme and 

 impetuosity au;:,ment( d. til tie}- iind their way through 

 the weakest pai't, and ca; ry the softer matters onward 

 by new cliannels, u'h;!c the moi'e ponderous frascmoits 

 remain behind By a prv)cess of this kind cont nuinj^ in- 

 ce-santly for ages, the beds of ancient torrents enlarge 

 ^■radually into vailles, and what w ere once sharp edges. 

 or hard bottoms of the streams, become slopes and 

 plains. The waters desceniiing from level to level, and 

 leaving at each resting place their grosser matters, gia? 

 dually dejiosit the lighter and more soluble ; thus cir- 

 cumscribing the ocean by continual accessions of sand, 

 mud and pebbles, ail of which are arrested and bound 

 together by the truiiks and brandies of trees. The 

 Mississippi olYers a luminous e-uniple of all these ope- 

 rations. It has been e<nnp!!ted by Liancourt that be- 

 tween 1720 and 1800 a period o'f eighty years, this river 

 has advanced its banks fit'teen miles into the sea. Thus 

 under the eyes of three generations, it has raised a new 

 eouuirv from the sea which daiiy encreascs, and where 

 beds of coa! ure slowly f(-'rniing, and accumulating for 

 the use of iulure ages. So rapidly does ilus deposition 



