NO. 1 GEOGRAPHICAL ACCOUNT AND STATION RECORDS 3 



primary purpose of the geographical account. If the word "mud" appears 

 often in describing the ocean bottom, or if "northeast trades" or "westerly 

 directed currents" seem unduly emphasized in describing surface and sub- 

 surface conditions, the reason is not only that these factors conditioned 

 the activities of the field workers during the entire month in which collec- 

 tions were being made but that, operating over infinitely longer periods, 

 they cannot but have been effective forces in conditioning the marine biota 

 of the southern Caribbean region. 



THE CARIBBEAN AREA 



The southern Caribbean has certain general characteristics as to wind, 

 land and sea temperatures, humidity, rainfall, and ocean currents which, 

 if presented at the outset, will not require later discussion. The region is 

 remarkably uniform in respect to the first of these, being entirely within 

 the latitudes of the northeast trade winds. It may be taken as axiomatic 

 that a vessel working eastward along the north coast of South America 

 will encounter head winds varying in direction from northeast to east. 

 It is the November-to-April period in which the winds blow most steadily, 

 or from 70 to 90 per cent of the time. The velocity of the wind is least 

 in October, just before the onset of the November-to-April period, and 

 greatest, at least in the southwest Caribbean, in May, June, and July. 

 This may account for a statement made by a Magdalena River Pilot that 

 the season of the northeast trades was nearer seven months than five in 

 the Barranquilla region. Wind velocity is greatest at noon, or shortly 

 thereafter, and least at sunrise, a fact that was taken advantage of by the 

 Velero III in dredging operations at Cape la Vela. 



Air temperatures are also remarkably uniform, with an annual mean 

 for sea-level stations of 79° to 81° F. September and May are warm 

 months, with mean temperatures of 81° to 83° F., while January and 

 February are cooler, with 76° to 78° F. mean temperatures. Extreme 

 high temperatures of 100° F. or low temperatures of 55° F. are seldom 

 encountered near the coast. These general figures for the entire region 

 would seem to be borne out by Velero III observations, all made in the 

 month of April, when air temperatures ranging from 70° to 84° F. were 

 encountered at sea or in open anchorage. A 90° F. temperature recorded 

 at Caledonia Bay, Panama, may be accounted for in part by the distance 

 of the anchorage from open ocean, and a 99° F. figure at Barranquilla, 

 Colombia, by the heat reflected from the steel surfaces of the ship and 

 adjacent steel and concrete whai-ves. 



