1186 



METEOROLOGY. 



[TUB OOT.F STREAM. 



parti of the ocean. The polar whale would deli-ht in the 

 t..rriil one, and tin- habitat of the pearl oyster would l>o 

 also under tin 1 iivl<en>, or in frigid waters colder than tlio 

 melting ice." Tlio particles of water being nml.il,-, the 

 ocean, and indeed aqueous collections generally, are 

 amenable to the same law of convection as wag descri!-- 1 

 when treating "f tho cause of winds. Hot water, being 

 pacifically lighter than cold wnter, must necessarily come 

 he surface ; and for every current in one direction 

 a must be a counter-current in tlio reverse din 

 precisely in the same manner as occurs in the develop- 

 ment of a wind. 



Contemplating tho ocean in its relation to the effects of 

 heat and motion, our original ideas concerning that vast 

 collection of waters are modified and expanded. Instead 

 of regarding the ocean as one shapeless aggregation of 

 liriny water, it presents itself to us as an assemblage of 

 many streams a network of mighty rivers, each follow- 

 ing its own course, each having its own temperature, its 

 own flora, its own animals ; and though devoid of pal- 

 palile hanks, scarcely loss accurately denned on that 

 account. Amongst all these oceanic currents, that 

 denominated the gulf stream is the largest in size the 

 most important in the functions it subserves. The gulf 

 stream is so far from being an imagining of mere theory, 

 that the dark blue alone of its waters suffices to point out 

 its limits and define its course. 



All hypotheses as to the cause of tlio gulf stream arc 

 as unsatisfactory as the direction of the stream itself, and 

 its benign influences are evident. The first idea relative 

 to the gulf stream was, that it originated in the impetus 

 given to the ocean by the disemboguement of the Missis- 

 sippi ; but placing out of consideration tho inadequacy of 

 this assumed cause, on account of the comparatively 

 small amount of water which even a river so vast as the 

 Mississippi can pour forth, it follows that, if really the 

 cause of the gulf stream, the whole Gulf of Mexico 

 should, in process of time, be found to contain only fresh, 

 or, at the most, brackish water. This, it is scarcely neces- 

 sary to remark, is not the case. Franklin advanced the 

 theory, that the gulf stream is referable to the pressure 

 of an inordinate amount of water against the coast of the 

 Gulf of Mexico by the trade winds an idea which is 

 scarcely more tenable than the last. 



'ver the cause of the gulf stream may be, the 

 direction of its current is obvious. Setting out from the 

 hot regions of tho Mexican Gulf and the Caribbean 

 Sea, it proceeds northward to the great fishing-bank of 

 Newfoundland, and thence to the shores of Europe, 

 yielding up its heat to the genial west winds, and thus 

 transferring a portion of the superfluous heat of the 

 tropics to our colder shores. The greatest heat of the 

 oceanic water of the Mexican Gulf is about 8i, or about 

 the ocean temperature duo to latitude alone, 

 r it has ascended to 10 of north latitude, the gulf 

 stream has still only lost 2 of the original heat with 

 which it set out. Ascending northwards a distance of 

 three thousand miles from its first origin, this mighty 

 oceanic river still preserves the heat of summer even in 

 winter time. It now crosses in an easterly direction, in a 

 lino coincident with about the fortieth degree of north 

 latitude, spreads itself out, and imparts to Europe a 

 genial temperature ; which mere latitude could never 

 give. The gulf stream now pauses in its course ; it is 

 split into two divisions by the British Isles, and two 

 gulf streams are formed. Of these, one ends northward 

 in the direction of Spitzbergen, while the second enters 

 the Bay of Biscay imparting temperature to each, ami 

 causing a soft mantle of vapour to arise, which, wafted 

 landward, in its turn disperses the heat of the gulf stream 

 far inland. Very little is known concerning the depth to 

 hi-h the gulf stream extends. 



Maury, of tho United States naval service, as- 

 sumes that depth to be two hundred fathoms ; and, 

 arguing on this assumption, ho calculates that the 

 niiioimt nl' heat h-d away from the Gull o by 



this >, on a winter's day, the whole 



atmosphere which hovers over Franco and the British 

 Jules, from tho temperature of : F. to about TIC ; in 



other n-onls, from wintor-eoM to summer h. it. I'.iit the 

 genial influence of the gulf stream on tho British N!es n 



V than this. Every western breeze that blow 



wards us crosses the mi ;litv gulf stream, robs it of a 

 portion of its heat, and comes towards our shores charged 

 with warmth and laden with balmy moistiir. 

 Ireland in a suit of green, ami imparting a mildn. 

 both England and Ireland which can be best appro- 

 when we consider that the roasts of Labrador, o: 

 American side, and under the same parallel of latitude 

 as England, are rigid with ice. In ls.'il, the harbour of 

 > -lohii's, Newfoundland, wa 



the month of .June ; yet the harlxmr of Liverpool, 

 though 2' further north, is never ice-locked, even in tin- 

 severest winte' vning to any chart of 

 thermal lines, tho current of the gulf titruam, as just 

 described, may bo readily tr 



Although the climaii f tho gulf stream is so 



advantageous to Western Europe, in >re especially to 

 these isles, it is scarcely less advantageous to the re 

 whence it originates. If the gulf stream be the channel 

 along which an amount of heat so considerable j, 

 eastward, we may speculate on the consequences 

 would have arisen had the amount of temperature, now 

 conveyed away, remained in the gulf itse'.f. Kv.-n now 

 tho coast-line of this region is extremely hot and un- 

 healthy ; how much moro hot and unhealthy would it 

 have been had the gulf stream not existed ! 



Under-Current of the < m. As the trade winds 



are only an under atmospheric current, passing |in an 

 opposite direction to a current above ; so the gulf 

 stream is only the counterpart of an inferior current of 

 cold water flowing back, to compensate for that which 

 has departed. Not only does theory proclaim this, but 

 it is borne out by experiment. At a mean depth of 

 two hundred and forty fathoms, an under-current of 

 water flows into the Caribbean Sea ; and the temperature 

 of this current has been found as low as 48, whilst tho 

 surface-water had a temperature of 85". At the depth of 

 three hundred and eighty-six fathoms the temperature 

 had fallen to 43; and at tho very bottom of the gulf 

 stream the temperature was only 38; hence the exis- 

 tence of the returning cold current is fully borne out. 1 1 

 comes, there is little reason to doubt, from the arctic 

 circle ; presenting the closest analogy to the lower aerial 

 current which constitutes the trade wind. 



The course and extent of the gulf stream were not 

 generally known until the celebrated Dr.- Franklin 

 drew attention to the subject. The history of this 

 event is worthy of narration, illustrating as it does the 

 discriminating and logical mind of that extraordinary 

 individual. 



Happening to be in London in 1770, his opinion was 

 demanded respecting a memorial presented by the Hoard 

 of Customs at Boston to tho Lords of the Treasury, 

 stating that tho Falmouth packets were generally a fort- 

 night longer on their voyage to Boston than common 

 traders were from London to Providence, Rhode Island: 

 whence their request that the Falmouth packets might 

 be sent to Providence instead of to Boston. "Franklin 

 could not understand the reasonableness of this request, 

 inasmuch as London was much further than Falmouth ; 

 and from Falmouth the routes were the same ; so that the 

 difference should have been tho other way. Desiring a 

 solution of his difficulty, ho consulted Captain Folger, a 

 Nantucket whaler, who chanced to be in London at tho 

 time. The whaler explained that tho difference arose 

 from the circumstance that Rhode- Island captains were 

 acquainted with the gulf stream, while those of the Kng- 

 lisli packets were not. The latter kept in it, and were 

 driven back sixty or seventy miles a-day ; while tho 

 former avoided it altogether." M<iry. 



The manner in which tho old whaling captain had 

 been made acquainted with the existence, tho ext 

 and the direetioii of this gulf stream, is curious en 

 in its way. His instructors were the objects of his 

 search, the arctic whalr* animals which, having a dis- 

 like to warm water, never enter tho gulf stream, though 

 they swim close up to it on both sides. 



