The Mediterranean Sea 



not affected by the pressure obtaining at great depths in the 

 sea. Fifty years elapsed before any similar experiments were 

 made, when D'Urville, in the "Astrolabe," made a few observa- 

 tions at the beginning and the end of his famous expedition. 

 There is some uncertainty about his observations in 1826 and 

 j, and also about the later ones of Berard in 1831, as we 

 are not informed whether the self -registering instruments used 

 protected from pressure or not. Mr Prestwich 1 , however, 

 who has collected and critically discussed all the older deep-sea 

 temperature observations, concludes from a comparison of 

 their results with those obtained by Aim6 with protected 

 instruments, that they were so protected, and admits their 

 ;!ts into his tables without correction. In the deep water to 

 the northward of the Balearic Islands, D'Urville found in 

 -4-5 1 . in 270 fathoms, and in March 1829 547 

 at the same depth, and the same temperature (547) in 530 

 fathoms. Berard, experimenting in the sea between the 

 Balearic Islands and Algeria, found the temperature of the 

 deep water nearly a degree higher, namely 55-4 F., in depth* 

 of 500 to 1000 fathoms. Ainie 2 relates his own careful experi- 

 ments on the temperature of both surface and deeper water in 

 leitjhbourhood of Algiers and discusses them in connection 

 with thos- of other observers with very great ability. He 

 concludes from his own observations and those of Berard that 

 uniform temperature at great depths is 54-86 F. From a 

 ation of the general climate of the Me liternnean. he 

 to the eoneluMon that the temperature in the deeper 

 tin- sea ou-ht t> be lower than the annual mean of the 

 ni'l thai it ouu'ht to be not very <lil(erent from the 

 6 temperature in the winter month-. From 

 observations at Toulon and Algiers, he finds that at neither 

 does the surface temperature fall below 50 F., and that 

 mean -urtace temperatures in the mouth- December, 

 lary, February, March, and April U at Toulon 53-06 F. 

 an.l at Algiers 56-84 F. The in. -an "I th ures 



.. whi'-h ta almost exaetlv what he MM.!- to be the mean 



1 I'hil. I i,t>: 187 P- 60I. 



-hys., 145, XV. p. 5. 



152 



