CLYDE SEA AEEA. 107 



both shores, and least in the centre. The isotherms dipped from the west shore up to 

 the surface, showing a greatly thickened layer of warm water against that shore. The 

 temperature of 47° left the west side at 5 fathoms, crossed the centre at 4 fathoms, and 

 curved up sharply to the surface at Station 6. While the isotherm of 46°'75 ran 

 parallel half a fathom deeper from the west shore to Station 4, whence it rose to 3^ 

 fathoms at Station 6, and thence dipped to 4 fathoms at the eastern shore ; the line of 

 46°'5 ran on the whole parallel and about half a fathom deeper, and below it the fall of 

 temperature was gradual, the isotherms being highest in the centre and lowest at both 

 sides. Two bands of close-clustered isotherms cross the section, showing two planes of 

 juxtaposition of layers of unequal temperature ; between these are the thoroughly mixed 

 areas, which occur on the west shore, in the centre, and on the east shore. On the west 

 side of the central line the temperature rises toward the west shore at every level, 

 showing a descent and banking up of the warmer upper layer. On the east side, from 

 4 fathoms to the surface the temperature was practically uniform, and cooler than the 

 rest of the surface, showing an upward movement, but more feeble than that in the 

 centre ; and below 4 fathoms the isotherms dip down from the' centre eastward as well 

 as westward, showing the descent of warmer water along the windward side. 



The natural conclusion to draw from this is that at about 5 fathoms the windward 

 side is divided into an upper zone of direct wind circulation, and a lower zone or eddy 

 of inverted wind circulation, as shown roughly on the diagram fig. 39, Plate XXIX., 

 while the leeward side has a complete system of direct circulation, the power of the 

 wind causing an upward current in the centre as well as against the shore. 



Observations at Shandon. — Soundings were made in mid-channel off Shanclon Pier, 

 in line with Ma-more Farm on the opposite side, in a depth of 21 fathoms. About 

 a quarter of a mile higher up, the greatest depth (23 fathoms) occurs. Sections are given 

 in Plate 9, fig. 17b, in Part I. 



The density of the water was as follows : — 



Surface (10 observations). Bottom (9 observations). 



Mean, 1-02233 102353 



Maximum, 1-02378 1-02398 



Minimum, 101914 102323 



The bottom water of the G-areloch is the least dense of any in the Clyde Sea Area, 

 excluding the estuary. 



The great range between the temperature of surface and bottom layers is noticeable, 

 particularly in the cases of maximum positive slope in early summer ; but the form of 

 the curves is of interest as well. Nos. 1, 5, 18 may be excluded from consideration on 

 account of the small number of observations made, and in the case of No. 5 on account of 

 the very exceptional form. No. 1 8 showed the maximum positive slope, 3° "6 in 20 fathoms, 

 but No. 12, with 3°"2, is more trustworthy. The maximum negative slope was 2°"4, 

 shown in No. 7. Both maximum positive slopes occurred in August (1887 and 1888) 



