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Show EMIGRANT'S GUIDE. As far as a residence of sjxteen winters, in the Mississippi territory an.d ]ower Louisiq.na, can enable the author of this treatise to judge, Mr. Dunb~r's obse rvations are accurat,e, and, if adopted as criteria, must confirm what has been already stated, that the winds of the Mississippi valley are too varjablt>. to prod~ce a general amelioration of climate, so far north as the basm of OhiO. Mr. Dunbar also records the fact, that the northwest \"''inds exert their influence as far as Natchez. Respecting the destruction of vegetables by frost, the cause ass ign-ell by l.VIr. Dunbar produces the greatest part of the effect; but there is another cause that must be very influential in such countries as .that ne ar N atclwz ; '"'here the e~tremes of s erility and fertility often approach within a few yarJs. In the rich low grounds . the juices of veuetables, particul arly cotton, are so abundant as to a1d the decom· po0s ing powers ot. f rost. . The fact mentioned by this respecta.ble author, of the d1ITerence of temperature between the sheltered high lands, and the exposed low· lands renders the correctness of the idea at least doubtful, that clearinu )~nds tend to ameliorate climate. l\1r. Dunbar has entered his m~n veto against th is conclusion; and well he might, as every phenomena in the country where his observations were maJe, was in oppo· !ilion to its adoption. And no country can be more completely suita· ble for sat is factory expe riment on th is very inte resting subject. 'I' his picture of the variations iH the air, to which we have be.e~ l(>r many y ears familiar, is in all its parts correct, and proves th.e Influence of the northwest winds in places far south of th~ bas1n of Ohio. The far ther '~'est the traveller advances from the Mississippi river, the more southern will he find this northern influence. The vast prairies of North America reach from the gulf of 1\fexico to ~be Frozen ocean, a distaBce of forty degrees of latitude, and followmg the obliquity of their course, near three thousand miles. . Part of this great grassy expanse is protruded into the Ohio basm, :m4 reaches to the south side of lake Erie. Rising from the surface of the Ohio and Mississippi rivers, and from that of the Canadian. Jakes, the country rises to the northwest into high table land, over whrch the winds have an uncontrolled motion, carrying with them to the foot of the Aleghany mountains, the refrigerating partic1es collecte~ from the dreary plains so emphatically described by Mr. Macke~z~e .an~ others. It is by the power of this frozen current that the MrsstsSIPP1 is se often frozen at St. Louis in Dece mber, and which render the Ohio river unnavigable two months of each year, almost to the mouth. We are ltd to believe, that advancing west from the Ale· gbany mountains, the inteflsity of the cold jncreases, and that tb,e sea· ~ons are at St. Louis more rigorous than at Cincinnati, though the former lies 30 minutes of latitude south of the latter. The peculiar local po-ition of Cincinnati afford a double advantage, sheltered. fr~r~ the north, and exposed to the south; the position of St. Louis IS dtreMt!! the reverse, but the frequent freezing of so rapid a river as the t:~i ! issippi, aQd at such an early season of the year, evinces a s.ener2 i11ten.it f:>f colu over the adjacent country. I EMIGRANT'S GUIDE. r .From th~ m?st authentic Jocuments it appears, that tbP. northwest w ~nd p_rev~lls 1? Dcc~mber, J anuary, and February* The re~son of th ts rer·Jal ~HJe 1s 1bvrous. On the approach of winter, those eternaiJy frozen regwns bey( nd 46° N. lat., where icy winus rarwe over the Jiaked dese rt , and from above 50°, where tl1t> frost-boun l ·eartb forbids the existence of wells ur springs, comes a volume of cond en ~ ed, and (llm~st congealeJ ai r, which l Jcks the rivers in fetters of ice often as fdf ou th n~ 35° north latitude. Warm weather iu the autum: 11al months, is constantly followed in a short time by' a col<.! northwest or north win d. 'I'his ilood of col 1 air in its motion to Lhe southe a~t its usual course flc~w~ down .the valleys of the Mi~souri .~mel Mi. sis:~ i~pi rivers, sweep~ ~net. the Ohw, an~ first meets nn nuped11nellt to its motion whE>n comwg m contact wrth the Alr.ghauy mountaihs. ItA progress b here arreste~ l Y_ two causes; first t.he mouuta ins themsel ves, and secondly, 1he mas~ ot cold and dense a1r upon these rnountains. The northwest. wmd thus interrupted in its direct cour~e, turned by its own ~.rav1ty to the ;;outb, rushes down the Miss iss ippi valley, an<.l often cartie: fr~s t suffic1enl to destroy the orange ~ rees on tlu'.! gulf of Mexico, and t? frec~e the ponds aud other .small bou1es of stagnant water near tbe Cl~~ ot ~ C\ Or!i•ans. . Allowmg to this ~reat current, a motion of tlm ty tmles per ho~r, .'t .would cross the continent, from the Frozen ocean to the gulf of M x1co, in about four Jays. Havinu fewer ob. s~acles w.estward than ea~.t ward of the Mississippi to itni~ede its advance ,, this m.:1ss of cold a.t r has protruded the limit of . snow farther ~muth m the former, than m the latter section of our con tinent. tl sa mt >b _ ervalw. n rm.g i 1t be made respectin()' fro~t but as the no t'h le borde~ uf t~1e ~ul~ uf Mexico is every wher~ subj~ct to frost, it :du~[~ of no 1utenor hrrut. ~ Tbe ~ptantily. of wat~r. tbat falls upon .the earth, in the form of rain, .e~, haJJ, ~nJ snow, dlller.s extremely m places situate<.! apparently 1Sundar. No~ only the extstence but the quantity of snow bas been ~?nnect~d w1th tile degn~e of _cold, experienced at a11y given place. I he ex1ste~ce of snow must of necessity depenJ uptiln a thermometri ~ al uepr~ sswn below _that .neceesa ry to permit a frust sufficiently vio-enl to freeze w~ter mto lee, or prevent its melting; but there is no a1~parent c~mnex10u between the intensity of cold and the quantit fi~t~no\v. Extremely seve!·~ frost often occurs without, or with ver~ t e s~ww; tl.1erefore, uo latr data is afforded as respects the tempera· 1i~:e 0 ~ ~ 11Y gn·en _ Place by an accurate re g i~ter of its snows, unless th t r.eg~;:,~er contdtnS a correct recorJ of the absolute depth of water ~t tails mall forms. R<1in and snow are mere relative terms. Al ~~{letl~er more ~r less moisture actually falls west than east of the t . o 1'-"1Y mol~ ! lallls, has never been determined with sufficient cer~~ mty to aur~ Jt a sa[e c~nclusion. J u lgiug from analogy, we should ti !~ose. t~lat Ill the mtcnor less moistu re does fall than on the Atlantions ecirvrty, on a r~ equal surface ; but that, of the respective proporteor tll snow to ram, we are fully pel·suaued more of the former me-s on the western, than does on the eastern section of our 41 Brake's Cincinnati, page 9!>. 3~ |