GULF STPtEAM, CLIHIATES, AXD COMMEnCS. 51 



their specific gravity in a state of perpetual alteration in consequence 

 The true cause of of tlic cliangc of saltuess, and in consequence also of 

 the Gulf Stream. j^i^q cliangc of temperature. In' these changes, and 

 not in the trade-winds, resides the power vrhich makes the great 

 ciuTents of the sea. 



CHAPTEE III. 



§ 150-191. IXFLUENCE or THE GULF STSExUI UPOK CLIMATES 



AND COMMEECE. 



150. Modern ingenuity has suggested a beautiful mode of 

 How the ^vashing- warming houses in winter. It is done by means 

 warmer'"'''''^ '' of hot watcr. The fm-nace and the caldron are some- 

 times placed at a distance from the apartments to be warmed. It is 

 so at the Washington Observatory. In this case, pipes are used to 

 conduct the heated water from the caldron under the superintendent's 

 dwelling over into one of the basement rooms of the Observatory, 

 a distance of one hundi-ed feet. These pipes are then flared out 

 so as to present a large coolnig surface; after which they are 

 imited into one again, through which the water, being now cooled, 

 returns of its o\m accord to the caldron. Thus cool water is 

 retm-ning all the time and flowing m at the bottom of the caldron, 

 while hot water is continually flomng out at the top. The ven- 

 tilation of the Observatory is so arranged that the cii-culation of the 

 atmosphere through it is led from this basement room, where the 

 pipes are, to all other parts of the buildmg ; and in the process of 

 this cnculation, the warmth conveyed by &e water to the basement 

 is taken thence by the air and distributed over all the rooms. 

 Kov/, to compare small things with great, we have, in the warm 

 waters which are contained in the Gulf of Mexico, just such a heat- 

 ing apparatus for Great Britain, the North Atlantic, and Western 

 Eiu-ope. 



151. The fm^nace is the torrid zone; the Mexican Gulf and 

 An anaiopry showing Caribbean Sea are the caldrons; the Gulf Stream 

 rl-ares teuipiratmi'^ is the couducting pipe. From the Grand Banks of 

 iu Europe.. Ne^\'foundiand to the shores of Em^ope is the base- 



ment — the hot-air chamber — in which this pipe is flared out so as 

 to present a large cooling surface. Here the circulation of the 



E 2 



