130 PHYSICAL GEOGRAPHY OF THE SEA, AND ITS METEOP.OLOGY. 



mitigated and made botli refreshing and IiealtliM by the alterna- 

 tion of those mnds which invariably come from the coolest place 

 — the sea, which is the cooler by day, and the land, which is the 

 cooler by night. About ten in the morning the heat of the sim 

 has played upon the land with sufficient intensity to raise its tem- 

 peratm^e above that of the water. A portion of this heat, being 

 imparted to the superincmnbent air, causes it to rise, when the air, 

 first from the beach, then from the sea, to the distance of several 

 miles, begins to flow in Viith a most dehghtfiil and invigorating 

 freshness. 



315. When a fire is kindled on the hearth, we may, if we will 

 Cause of land and , obsorve the moats floating in the room, see that 

 sea breezes. tlioso ncarost to the chimncy are the fii'st to feel 

 the draught and to obey it — they are drawn into the blaze. The 

 circle of inflo^dng air is gradually enlarged, until it is scarcely 

 perceived in the remote parts of the room. Now the land is the 

 hearth, the rays of the sim the fire, and the sea, with its cool and 

 calm air, the room; and thus we have at ouj* fii'esides the sea 

 breeze in miniatm^e. When the sun goes down, the fii'o ceases ; 

 then the dry land commences to give off its surplus heat by radi- 

 ation, so that by dew-fall it and the air above it are cooled below 

 the sea temperatm^e. The atnlosphere on the land thus becomes 

 heavier than on the sea, and, consequently, there is a wind sea- 

 ward which we call the land breeze. 



316. "A long residence in the Indian Archipelago, and, conse- 

 i.icut. jansen on the queutly, in that part of the world where the inves- 

 irthnndTan Archi! tigatious of the Obscrvatory at Washington have not 

 p^^^so. extended, has given me," sa^^s Jansen,* in his 

 Appendix to the Physical Geography of the Sea, " the opportunity 

 of stud}ang the phenomena which there occur in the atmosphere^ 

 and to these phenomena my attention was, in the first place, 



* I have been assisted in my investigations into tliese phenomena of the sea by 

 many thmking minds ; among those whose debtor I am stands first and foremost 

 the clear head and v\'-ann heart of a foreign officer, Lieutenant Marin Jansen, of 

 the Dutch Navy, whom I am proud to call my friend. He has served many years 

 in the East Indies, and has enriclied my liumble contributions to the " Physical 

 Geography of the Sea" with contributions from the store-house of his knowledge^ 

 set oif and presented in many fine pictures, and has appended them to a translation 

 ')f tlie first edition of tins work in the Dutch language. He has added a chapter 

 on the land and sea breezes ; another on the changing of the monsoons in the East 

 Indian Arcliipelago : he has also extended his remarks to the north-we^t mon- 

 soon, to hurricanes, the south-east trades of the South Atlantic, and to winds and 

 currents generally. 



