THE VOYAGE OF H.M.S. CHALLENGER. 
r.4 
... s > which was almost the only navigation known to the ancients and up to the middle ages. 
\ . irh a the fifteenth century the Portuguese discovered the Guinea current ; Vasco 
l.i'UKcm J jo 
- a (buna must have noticed the Mozambique current. In 1513 Antonio d’Alemanos 
c - rveil the cuiTeut of the Gulf Stream near Florida, and Varenius, as far back as 1650, 
pia ••• the source of this current in the Caribbean Sea. 1 From Sir Richard Hawkins’ 
observations it is evident that the Gulf Stream had already been observed in the northern 
par s of the Atlantic between Newfoundland and Europe. It is probable that, as early 
, 14 07, Sebastian Cabot observed the Labrador current, while the first navigators who 
ventured into the Pacific had to grapple with the cold current of Peru, as shown 
by their log-books. 
I. .n lo da Vinci, in explaining the currents running from the equator to the poles, 
said tie v were produced by an elevation of temperature, which expands the water, and 
would make an equatorial swelling were the waters unable to flow away by the currents, 
u id thus " --establish the equilibrium of the surface of the sea. The cold currents from 
the j wiles to the equator had been explained in the seventeenth century by the great 
evaj -ration of the water in the tropical zones, which had to be balanced by water 
brought from higher latitudes. We may add that, even at that period, the salinity of 
the tropical waters was attributed to the same cause, viz., evaporation. The current 
ow trds the w--st, which had already been observed by Columbus, was interpreted as 
being in accordance with the rotation of the earth, not, however, in the sense of 
Copernicus, but by supposing the liquid envelope of our planet to be drawn from east 
to west by the movement of the “primum mobile” of the Ptolemaic system of 
astronomy. 
In 1665 Athanasius Kircher traced on a map all that was then known of marine 
■ •unviits. J. Vossius discussed this important question, and collected together all the 
information extant in his time. He points to a “ motus perpetuus ” in the torrid zone, 
whi'-h follow.- xactly the course of the sun, and becomes more pronounced between the 
■ oa-t of Peru and the Moluccas; he also mentions a second similar motion running in a 
outlu-rn dir- < tion, dependent on the sun’s movement, but modified sensibly in its course 
by t’-<- configuration of the African coast; and, lastly, he speaks of a “ motus tertius 
[ i >ri -• mpr-r contrarius,” of which the Gulf Stream forms part . 2 Fournier, in his great 
w<>rk on hydrography, had, it is true, twenty years before Vossius given a careful list of 
all t!i« lo ditii to the number of twenty, where currents had been noticed, but he had 
f"rnwd in- th< oi y to explain these phenomena. We know of no really important addition 
to this subject during the eighteenth century. 
M - .Mini impetuous intf-r Gubam et Jucatan illabitur marc, aftluitque inter Cubam et Floridam ’’ 
fVtrvnnu, Gvographi* gencrali*, ('ami-., 1672, p. 119). 
* Vomi':>, !►«* room man urn ct rentornm liber, Hagn- Comitum, 1603, pp. 1, 4, 8. 
’ 1 r - II if -aj.b :<• < nt. nt la tin-one ct la pratique <lc toutes lea parties rlc la navigation, Paris, 1643, 
p 478 
