CLYDE SEA AREA. 109 



peculiarities. The curve of mean temperature is a straight line passing through the 

 surface, centre, and bottom of the S. In the positive curve the upper 10 fathoms 

 show temperatures below the mean curve, the lower 10 fathoms show temperatures 

 correspondingly above the mean. The positive curves of this type occurred in June and 

 August, the negative in November. They show typically in summer rapidly warming 

 surface and bottom water, and a large mass of nearly uniform temperature between, 

 colder than the surface and warmer than the bottom layer. 



The mean temperature of 20 soundings (12 in the summer, 8 in the winter half- 

 year) was 48°, maximum 57°'4 in August 1887, minimum 41 0, 4 in April 1886. 



Partial Cross-Section on June 7th, 1888. — At 12 h 15 a sounding was made at the 

 deepest point in mid-channel, and at 12 h 40 another off Shandon Pier in 6 fathoms. 

 The former showed much higher temperatures at the same depth, the isotherms sinking 

 abruptly to windward. At 15"40 a sounding was made in 4 fathoms off the pier, and 

 at 16 h 10 another on the western and leeward shore directly opposite. This showed a 

 well-marked rise of temperature on the leeward as compared with the windward shore. 

 In the three hours, however, the temperature off Shandon had risen 1°, and the dip of 

 the isotherms was altered. Hence the section which was drawn cannot be compared 

 with that off Clynder, although it appears to show similar features in a less marked way. 



On October 22nd, 1888, at ll h 20, wind R, very light, and on October 25th at 

 ll h 10, wind S.W. by S., a stiff breeze, observations were made with great com- 

 pleteness. The mean temperatures as deduced from these curves was practically 

 the same, 49°"9 for the former, 50 o, for the latter, so that, on the whole, they 

 represent a complete cessation of cooling during three days in Autumn. The average 

 temperature of the lowest 5 fathoms was unchanged, that of the superficial 5 fathoms 

 was uniformly raised by o, 2, a result probably due to the surface action of the strong 

 wind blowing up the loch on the second occasion. The intermediate layer was slightly 

 cooler on the second occasion, evidently showing that in the three days there had been first 

 cooling down to at least 10 fathoms, where it must have amounted to more than 0°"1, 

 and subsequently a uniform warming of the surface layers. 



The relation of change of temperature to depth and time at Shandon is shown in the 

 diagram fig. 9, PI. V., in which the tendency towards homothermic change of tempera- 

 ture is made evident. Only at the maximum of 1887 and 1888, and at the minimum of 

 1888, are there clear traces of change of temperature taking place much more rapidly on 

 the surface than at the bottom. 



Observations at Garelochhead. — Soundings were made in mid-channel, ^ of a mile from 

 the head of the loch in a depth of 10 fathoms, shoaling rapidly to the head. (See section 

 17a, PI. 9, in Part I.) The average density of the water at this station was as follows : — 



Surface, 11 observations. Bottom, 9 observations. 



Mean, 102238 .... 1-02339 



Maximum, 1-02390 .... 1-02396 



Minimum, 101913 .... 102287 



