490 HYATT'S REVISION OF THE 



on the shore of Morocco and Barbary. According to Berghans, at Palermo, in Sicily, the 

 average winter temperature is about 52°. 3 Fahrenheit, 11°. 3 Centigrade ; at Naples, the next 

 warmest locality noted in the Western Mediterranean, it is 49°.2 Fahr., 9°. 8 Cent. All the 

 more northerly parts on the coasts of Italy, France, or Spain, have a lower average winter 

 temperature, including Cagliari, on the southern shore of Sardinia. 



According to Admiral Smyth, the lowest aerial temperatures recorded were 36° in Sicily 

 and 34° in Sardinia, and he gives for the " middle latitudes " of the Mediterranean a varia- 

 tion of from 50°. 1 to 44°. 3 for January, an isotherm of 46°. 2. This of course refers to the 

 Western Basin, where these observations were made, and accords quite closely with the 

 aerial isochryme of 50°, as laid down by Schouw, which runs a little south of the central 

 parallel of 40° in the Western Basin. With an aerial isotherm of 46° or an isochryme of 50°, 

 it may be assumed with great probability that the water at the depth of 30 fath. would not 

 be above 55°, since even in summer, at this depth, near Malta and in the extreme western 

 station of Carpenter, the temperature does not range above 63°, and remains at 55° at 100 

 fathoms in two localities. It will be seen farther on that this temperature, though lower 

 than that of the coasts of Barbary and Morocco, is not sufficient of itself to account for the 

 absence of commercial qualities of the Spongige from Sicily, Sardinia, and the southern 

 coast of Spain. 



The more northerly parts on the southern shore of the same basin have a considerably 

 higher average ; thus Algiers, according to Berghaus, has an average winter temperature 

 of 54°. 3 to 61°. 7, or about 58°, which is probably the correct mean, and in Schouw's map 

 by Berghaus, it stands nearly upon the isochryme of 54°. 



Tunis and Cairo, to the westward, have still warmer climates. Admiral Smj-th gives the 

 following temperatures ; at Algiers, 86°.8-41°.5; at Tripoli, 92°.5- 51°.2. No mention is 

 made in any authority to which I have been able to gain access of such cold weather as 

 undoubtedly is not infrequent even in southern Italy, Sicily and Sardinia, and the whole 

 shore from Tripoli to Syria lies close to the isochryme of 57°. 



The condition and inferior quality of the sponges on the Algerine coast show that here 

 we have reached the extreme limits of their habitat, and the average winter temperature 

 of the surface water, according to Admiral Smyth's allowance for variation, would be 

 58° + 1°.5 = 59°. 5, a result Avhich accords very closely with Schouw's map, and the ob- 

 served deep water temperatures in the Western Basin and near Malta, at 100 fathoms. 

 These calculations would seem to be very favorable to the view that both the bathymetrical 

 and the geographical distribution of the Spongite were limited by the minimum tempera- 

 ture of 55°, but there are other localities to be considered.^ 



The area of the earth's surface drained by the rivers which flow into the Black Sea, 

 amounts, according to Carpenter, to 939,000 square miles, while its own area, and that of 

 the Azoff Sea, is only 172,500 square miles, and its connection with the salt waters of the 

 Mediterranean is limited to the narrows of the Bosphorus. Under these circtmastances it is 

 not remarkable that its salinity or density, as compared by means of its specific gravity 

 with that of ordinary sea water, should vary from 1.012 to 1.014, and be less than half that 



1 Admiral Smyth is probably in error with his deep sea counted for; the averatjc being, according to Smvth, 42° to 

 temperatures. The discrepancy between his statements and 43° below 180 fath., while 55° is the lowest given by the 

 those of Spratt and Carpenter cannot be otherwise ac- other authorities. 



