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Sect. IX.l 



3IETEOROLOGY. 



311 



flat bases of cumular clouds from two ships wlsose distance 

 is Ivnown, or otherwise, should be seized when they offer. 



suddenly clouds over, or when f-rgs 



When the 



form unexpectedly, the barometer and thermometer 

 should be noted minutely, as such appearances often 

 residt from, a rapid diminution of atmospheric pressure 

 and consequent absorption of heat by the rarefaction of 





the air. Fogs prevailing at definite localities indicate 

 temperature of the sea habitually exceeding that of the 

 air. Thoy often also indicate the vicinity of ice. When- 

 ever fogs are met with at sea, the temperature of the air 

 and (^f the surface water should he recorded with more 



than usual care. 



Temperature of the 5t^a.~Shoals cast up water from a 

 lower level to the surface where any current exists, and 

 therefore a sudden change of temperature of the surface 

 may indicate a shoaL In crossing currents coming from 

 w^armer or colder latitudes^ the surface temperature 

 should he especially attended to, and the maximum of 

 irregularity due to the current watched for. Should 

 opportunities offer of obtaining deep sea temperatures^ 

 they should be eagerly seized. 



Observations in Port or in 



h..^ 



asccnam 



Teiyiporary Rei 

 Shore. — Opportunities should not be lost of 

 lofty eminences, and noting thereon the hygrornetrio and 

 thermometric conditions corresponding to altitudes mea- 

 sured by the portable barometer, or otherwise known. 



The temperatvire of deep wells should be ascertained, 

 and that of the soil at different depths, which, if made 

 with due care and under favourable circumstances, is an 

 observation of very ^rreat interest. Excavations should 



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