Page:Quarterly Journal of the Geological Society of London, vol. 27.djvu/80

 communication with the Polar seas, the case must assume a very different aspect.

Dr. Carpenter in his last cruise made also a number of observations in the Mediterranean, showing that while the surface-temperature in August and September varied from 69.5° to 77°, it fell in all cases to about 56° at a depth of 600 feet, and maintained that temperature through all the depths below that line. This confirms the experiments made in 1840-1845* by M. Aime, who found that the average temperature of the sea at a distance from land, for the twelve months of the year, was 64.4° Fahr., that of the air being 64.8°; and that the former decreased gradually to 54.6° at a depth of 1148 feet, below which to a depth of 4050 feet it was not found to vary 1°†. He considered that the diurnal variation of temperature ceased at 59 feet, and the annual variation at from 1148 to 1640 feet, although, in fact, his tables show little variation after 656 feet. The mean shore-temperature of January, February, and March, taking together the two stations of Toulon and Algiers, was ascertained to be 54.8°, with which the temperature of this part of the depths of the Mediterranean corresponds almost exactly.

The subject of the currents and temperatures of the Mediterranean engaged also the attention of Captain Spratt for a series of years, and a number of carefully made experiments are recorded by him. He also determined that while the temperature from the surface to a depth of 12 feet ranges generally from 76° to 84° Fahr., gradually decreasing to a depth of 600 feet, there was little variation below that line, and that the temperature of the depths of the eastern basin of that sea is about 59°, and of deep seas off Greece 55-1/2° — that while on the Mediterranean side of the Straits of Gibraltar there is a deep-sea temperature of 59°, there is one of 39-1/2° on the Atlantic side‡.


 * Ann. de Chimie et de Physique, 3rd ser. vol. xv. 1845.

† The following is M. Aime's summary : —

" Temperatures moyennes annuelles de la mer a diverses profondeurs.

Temperatures. Maxima des variations entre les moyennes mensuelles.

a la surface 18.2° C 10.2° C.

a 25 metres 16.3 6.3

a 50 ,, 14.4 2.8

a 100 ,, 13.7 2.0

a 200 „ 13.0 1.0

a 350 „ 12.6 0.0"

‡ British Assoc. Report (Sections), 1848 ; and ' Travels in Crete,' vol. ii. p. 345.