392 PHYSICAL CONDITIONS OF 



weighings in 30 samples collected on one trip. The results are not easily 

 explained or accounted for. It is quite clear on expressing the amounts of 

 sulphuric acid and alkalinity in terms of unit weight of chlorine (so as to 

 eliminate differences due to mere variations in salinity) that the water of the 

 Clyde Sea-area differs materially from that of the open ocean. By Professor 

 Dittmar's analyses of 77 ocean-waters he found the average ratio of sulphuric- 

 acid (SO 3 ) to chlorine to be 0'115S. Mr. Dickie found in the Clyde Sea- 

 area an average of 0'1172, and Mr. Dickson 0'1189. This indicates an excess 

 of sulphates due either to the addition of river-salts or to impurities in the 

 water, and the alkalinities, which are also greater than in ocean water, point 

 in the same direction. Taking all the observations the averages according to 

 vertical position are as follows : 



Samples from Dickie. Dickson. 



Surface, 0'1171 0'1185 



Intermediate, 0'1173 O1191 



Bottom, 0-1172 0-1192 



This shows some evidence of an increase of sulphates relative to chlorides 

 with depth, i.e. with salinity ; in other words the less land-water the more 

 sulphates a paradoxical conclusion. No definite relations of the sulphates 

 or alkalinity to position can be made out ; the results of the chemical 

 analyses showing a far greater change from time to time than from place to 

 place. The averages for the different trips work out as follows : 



Date, Nov. 1886. Feb. 1887. March 1887. May 1887. 



Surface, (12) 0'1174 (6) 0'1175 (4) 0-1175 (7) 0'1177 



Interm., (3) 0'1172 (3) 0-1175 



Bottom, (14) 0-1173 (7) 0-1176 (6) 0'1173 (8) 0'1176 



Date, June 1887. Sept. 1887. April 1896. 



Surface, (8) 0'1177 (14) 0'1161 (13) 0-1185 



Interm., (7) 0'1191 



Bottom, (8) 0-1177 (14) 0'1163 (9) G'1192 



The figures in brackets are the number of samples of which the result is 

 an average. 



Deposits. The deposits on the bed of the Clyde Sea-area are mostly 

 sands on the shallows and mud in the deep water. They have been studied 

 to some extent by Mr. J. Y. Buchanan, who found evidence of the effect of 

 the masses of chemical-works refuse which for many years have been 

 discharged into the water of the Area. He found a very considerable 

 proportion of sulphur, chiefly in the form of ferrous sulphide, in the muds of 

 the deeper basins ; and at several points, especially in the Arran Basin and 

 on the Bute Plateau, there were numbers of nodules mainly composed of 

 oxides of manganese and iron, quite similar to those found in the red clay of 

 the greatest ocean depths. The sulphur in the deposits may possibly account 

 for the increased proportion of sulphates in the deep water. 



Thermal Conditions. While there is a certain individuality in the 

 thermal regime of each physical region due to its individual configuration, a 

 general idea of the seasonal march of temperature in the water may be given 

 by considering the North Channel, the Arran Basin, and the deep lochs, as a 

 group represented by Loch Goil, which is a very good specimen of the type. 



On account of the thorough tidal mixing of the water in the North 

 Channel the temperature at any time is the same from surface to bottom, and 

 all seasonal changes of temperature take place simultaneously throughout 

 the whole depth. From the annual minimum of temperature in March, 

 about 42 or 44, the water in the Channel warms up steadily and gradually 

 to about 56 in September, and cools again uniformly for the next six months 

 (see curves in Fig. 2). All the water carried in to the Arran Basin by the 



