Observations in the North Atlantic. 349 



of rain. After the most violent part had passed, a hot parch- 

 ing gust of wind was experienced, which, in its turn, was im- 

 mediately followed by a cooler breeze ; and this alternation 

 occurred several times. I observed the thermometer as high 

 as 78°-7 in one of these gusts, and almost immediately after it 

 fell to 70-8 ; but I feel certain that, during some of the first 

 of them, the temperature must have been greater. Soon after 

 this squall, the clouds broke, and the wind settled at SSE., 

 but continued slightly squally, and with occasional hot puffs, 

 all the afternoon. The fall of the dew-point from 9 A.M. to 

 3 P.M. is worthy of notice. 



On the morning of the 20th March, when about 700 miles 

 from the nearest land, a hot breeze was again experienced, but 

 to a less extent ; while it lasted, the dew-point was very low, 

 and a peculiarly parched sensation in the nose and throat 

 was felt. Towards afternoon the parched sensation went off, 

 and. as may be seen in the table, the dew-point rose consider- 

 ably. 



The trade-wind commenced on the evening of the 15th 

 March. Tlie dew-point fell considerably lower next morning 

 than it had been for some days before with the south-easterly 

 winds. The same combination of a high dew-point with SE. 

 winds is noticed all over the Mediterranean, and also right 

 across the Atlantic. 



The variations in the temperature of the sea were noM'here 

 very great. There was an increase of 2°.7 on the 11th, after 

 which it fluctuated slightly until the 18th and 19th, on which 

 it increased 3^-0 and l°-7 respectively. A marked increase of 

 temperature occurred also on the 22d and 23d, after which it 

 went on gradually and regularly until the 31st, Avhen, the ship 

 having got into the equatorial current which sets along the 

 coast of South America to the NW., it rose l"-0 from the pre- 

 vious noon. During the month of April, wliile lying at Bar- 

 badoes, the temperature of the water in Carlisle Bay, half a 

 mile off shore, and in 17 fathoms, was found, from the mean 

 of five observations, to be 79'-3. On the 2d April, the sur- 

 face water in the sun was 79°-3, wliilc at the depth of 17 fa- 

 thoms it was 78''-7- On the same day, with a fresh trade blow- 

 ing, the surface water in the ship's shadow was found to be 

 decidedly lower in temperature than that at the depth of 3 or 

 4 feet, evidently from the evaporation going on from it while 

 within the shadow. 



