488 HYATT'S REVISION OF THE 



show considerable clifFerence in the temperature of the water during the months of August 

 and September in the two basins. At the depth of thirty fathoms, the limit of bathymetri- 

 cal distribution for the Spongia?, the water of the Western Basin was 63° to 66° Fahr., while 

 in the Eastei-n Basin it was from 66° to 68^. Dr. Carpenter's observations were made dur- 

 ing the prevalence of very hot weather in the Eastern Basin, and in the western part of the 

 Eastern Basin. Fortunately, however, other observers have remarked the higher general 

 temperature of the Eastern Basin. Capt. T. Spratt^ and Capt. Nares^ also give tables from 

 which we copy and deduce (p. 489) the following temperatures for the thirty fathom line. 



It will be readily seen by the table that the conclusions of Dr. Carpenter, that the East- 

 ern Basin was relatively to the Western of a somewhat higher temperature, is true of 

 corresponding seasons of the year, but is subject to certain local variations, as pointed out 

 by Capt. Spratt's observations, near Ci-ete, where he finds 59° at 50 foth. in September, 

 against 59°. 7 in August in the Western Basin, and 56° near Malta, in September. It is 

 probable, also, that in this locality the winter temperature at thirty fathoms would average 

 very nearly what it does in the Western Basin at the same depth, since even in June, with 

 the air at 80°, it holds a temperature as low as 68°, within 5° of the extreme western station 

 of Carpenter. In the Grecian Archipelago, also, the deep water temperature of 56° comes 

 up to the one hundred fathom line, and shows again an approximation to the lower temper- 

 ature of 55° near Malta, and at Station 1 of Carpenter at the same depth. This is import- 

 ant to the present subject, since in the Grecian Archipelago one of the finest qualities of 

 Sponcjla officinalis is found, but SjJongia equina is rare, and of an inferior quality, accord- 

 ing to Von Eckhel. Though in the soundings this cold water does not reach the fifty 

 fathom line, it becomes quite probable that in the winter months it very often rises as high 

 as this. 



Admiral Smyth's^ work on the Mediterranean, which also confirms these remarks, is 

 very instructive on other points, which it is necessary to consider before proceeding farther. 

 This author states that the average diSerence between the temperature of the surfiice 

 water to the depth of eight fathoms, and the temperature of the air, both taken at the 

 same hour, is about 3°. 5 colder for the summer, and 1°.5 Fahr., warmer for the winter. 

 This appears to be very small, but it will be observed in the table that in siunmer the 

 difference must frequently be very slight between the surfiice and the air where the ther- 

 mometer stands near 70°, or in winter, when it is about 60°. 



The difference of temperature between the Eastern and Western Basins of the Mediter- 

 ranean may possibly help us to account for the peculiar distribution of the commercial 

 sponges, and their partial absence from the Western Basin. They are found on the Dalma- 

 tian shore of the Adriatic, as fiir as Triest, and on the shores of Tunis, Barbary and 

 Morocco, as far as Ceuta, but not elsewhere in the Western Basin. If we take into consid- 

 eration the observations of Admiral Smyth with regard to the relative temperature of the 

 air and surface water, and remember that the latter, to the depth of 30 fiithoms in a com- 

 paratively still sea, like the Mediterranean, must be constantly influenced by the seasons 

 whenever there are no constant currents, and no proximity to a large body of colder and 

 deeper water, these difficulties will, in a measure, disappear. The winters along the shores 

 of Spain, France and Italy, are quite severe as compared with the corresponding periods 



1 Peterm., Geogr. Mittheil., 1862, p. 431, and Nautical Mag- -Proc. Royal Soc. Vol. xx, p. 97. 



azine. ' The Mediterranean. London, 8vo. 1854. 



