582 



Dr. W. B. Carpenter on the [June 13, 



" through the hot season will carry the elevation of temperature further 

 " and further down ; but so soon as the temperature of the Air falls much 

 " below that of the Sea, the surface-layer being cooled will become heavier 

 " and sink, and will thus carry down cold instead of heat." Now as Series 

 IV. was taken not merely eight days later than Series III., but also con- 

 siderably nearer to the northern coast of Africa, from which a hot dry wind 

 was continually blowing, I am inclined to believe that this remarkable 

 downward extension of a temperature as high as the mean between the 

 surface-temperatures of Nos. I. and II. is attributable to these accidental 

 influences, the local effect of which would be very little interfered with 

 in this part of the Mediterranean by any horizontal movement of water, — 

 neither tides nor currents having any considerable force along the Tripoli 

 Coast. — It may be hoped that as Serial temperature-observations down to 

 100 fathoms can be made with very little difficulty or expenditure of time, 

 such observations may be systematically prosecuted in different parts of the 

 Eastern basin, so that it may be ascertained what are the conditions by 

 which the rate of reduction of temperature from the surface downwards is 

 determined. 



72. Density of Water. — It might be anticipated that a higher density 

 would prevail in the Eastern basin of the Mediterranean than in the Western, 

 for two reasons :— first, that the hot and dry winds of the Libyan desert, 

 unchecked and untempered by the interposition of any mountain-range, 

 would produce a greater evaporation from its surface ; and second, that 

 the reduction produced by the inflow of Atlantic water would scarcely 

 operate at so great a distance. Accordingly the analyses of Prof. Forch- 

 hammer gave a larger proportion of saline matter in the water to the east- 

 ward of Malta ; and my own determinations of Specific Gravity lead to 

 the same result. These observations, which were frequently repeated upon 

 surface-water as we proceeded eastward from Malta, did not at first indicate 

 any decided increase in density ; for in the previous year (Report for 1870, 

 § 92) we had found the Sp. Gr. of the surface-water in the neighbourhood 

 of Sicily to average 1*0280, sometimes rising as high as 1*0284; whilst 

 between Malta and Crete we now found it to vary between 1*0284 and 

 1*0288. The Sp. Gr. of the sample brought up by the water-bottle from 

 the depth of 2000 fathoms, in the Sounding taken on the 3rd of October 

 about 100 miles to the east of Malta, was 1*0291 ; thus being slightly in 

 excess of that of the surface-water, which was 1*0288. In the deep 

 Sounding taken eight days afterwards, not far from the Gulf of Solloom on 

 the Libyan coast, the density was found still greater ; the Sp. Gr. of the 

 bottom- water obtained from a depth of 1G50 fathoms being 1*0294, while 

 that of the surface-water was 1*0293. In another Sounding taken on the 

 following day nearer the coast of Africa, the density of the bottom-water at 

 a depth of 365 fathoms was found to be much more in excess of that of 

 the surface-water ; the Sp. Gr. of the former being 1*0302, while that of 

 the latter was only 1*0294. These results agreed in a very marked manner 



