METEOROLOGY.— TEMPERATURE. 477 



In the State of stability to which the surface of the globe appears 

 actually to have attained, the sun must be considered as the agent 

 wS most directly i.!li>..-s the temperature ot our atmosphere. 

 T^en^tl ot 1 e ky, tl:e na.nber of hours during which the sun is 

 above tii^io coupled with the height to -^ich he asee^^^^^^ 



such is the cause with which the temperature of each particular lati- 

 tude s pi'imarily connected ; and, in looking at the subject practi- 

 cahy it found to be so precisely ; not only is the mean tempera- 

 tuiif the year dependent L the length of thedays, af «- --^;- 

 altitude of the sun, but the mean temperature ot eadi month in the 

 year is essentially connected with the same eircumstances L the 

 iorthern hemisphere, the temperature rises from j^bout the middle 

 of January, slowly at first, more rapidly in April and May, to reach 

 Us maximum point hi July and August, when it begins to fall agam 

 until mid-January, when it is at its minimum. , i :,. 



The hi-lest iBcan annual temperature is, of course, observed m 

 the ii^^Borhood of theequator /between Qo and 10° or 120o lati- 

 tude on either side, at the level of the sea, where besides the equa - 

 ty orday and night, the sun, always elevated, passes the zemt^i 

 twice a vear. The observations that have been made up to this 

 time lead us to conclude that this temperature oscillates between 

 oao nnd '20O cent : 78.8^' and 84.2° Fahr. 



"\t! eaHh present unvarying uniformity of -face no^^-^^ 

 with reference to elevation but to constitution, so that th^ ^wer «f 

 absorbin- and of radiating heat should be everywhere alike, the cli- 

 mate o a place would depend almost entirely on its geographiced 

 Bositioi the points of equal temperature would be found on the 

 r.me pL^lle^^ latitude, or, to employ the happy expression mtro- 

 dS W M de Humboldt, the Mermal lines would all be parallel 

 wlhthJequator. But the surface of our planet is covered w^^^^^^^^^ 

 dulations and asperities, which cause i. «. ^^^^^^^^^ ^ J^selt of slnd 

 and then the soil is dry, or swampy ; it is ^,^^3f,^''!^,\tll th^ 

 or covered with umbrageous and ^^V^'^'^^j'J^^^^^^^ 

 causes corresponding varieties in climate, foi J^^ ^/^^^^'^.fcond?- 

 heatedin diffluent degrees as it is m one or « ^^J^ .^^ ^^\^^^^^^^^^ 

 tions. Another very important consideration is hat the surface ^s 

 a continent, or an island in the ocean : the cl mate of ^ ^o^^^^^' ^^ 

 a district, is vastly influenced by Its FO'™^>t^ "[^.^^^ mass S 

 thp ^-1 The difficulty, the slowness, with which such a mass ui 

 "uiras th'^ccanboL^es either heated or cooW,.*e cause f 



the temperate character both o'l t'>^f ™"='? ^"^""il's^^lifc 

 shores it bathes, and the islands of moderate <l™™s.on« ^/" ,7"^ 

 As we penetrate great continents from «« J^,^*""^' J^J^e S 

 the temperature both of summer and ^'"tei- hec«mes eurem^^^^^^ 



the uufefenee between the "^a" -3'^;,^°^, Xch have cSra- 



i"-sV;tHl:^hrs^^^^^^^^^ 

 ic^.^V::^^^s^-^ rra™ L-i';:^^"; that 



