32 



DR HUGH ROBERT MILL ON THE 



The observations made in the Estuary were too few and scattered to be worth 

 separate consideration, while those in Campbeltown Loch, the Holy Loch, Loch Long, 

 Loch Ridun, and the Kyles of Bute are also not considered, partly because the positions 

 were not characteristic, and the same order of phenomena was better illustrated by one 

 of the other divisions which was fully treated. 



The North Channel. 



In some respects the Channel is the most important of the physical regions studied, 

 and of all parts of the Area it is the one where observations should have been made 

 most frequently. On account of the small size of the " Medusa," and the rough state of 

 the water caused by tidal races and ocean swell, it was only on a comparatively small 

 number of occasions that full observations could be secured. An effort was made as a 

 rule to obtain soundings off the Mull of Cantyre, where the Atlantic water is quite 

 unaffected by the shore. When this was impracticable, it was often possible to observe 

 off Deas Point, about 1\ mile from land, but when, as was usually the case in winter, 

 it was unsafe to pass through Sanda Sound in the " Medusa," observations had to be 

 made at a point about 5 or 6 miles south of Sanda. Here the water was over 50 fathoms 

 in depth and fairly beyond the Great Plateau. In the summary of observations given 

 in the table, these three stations are indicated respectively by the initials C, D., and S. 



Table V. — Temperature Observations in the Channel. 



No., . . 



1 



2 



3 



4 



5 



6 



7 



8 



9 



10 



11 



12 



13 



14 



15 



16 



17 



18 



Date, . . 



16.4.86 



16.4.86 



19.6.86 



12.8.86 



22.9.86 



25.12.86 



30.3.87 



4.5.87 



5.5.87 



17.6.87 



18.8.87 



21.9.87 



8.12.87 



31.12.87 



16.2.88 



17.3.88 



21.3.88 



31.3.88 



No.of Pts. 



9 



9 



10 



13 



10 



6 



6 



9 



7 



12 



6 



6 



9 



6 



9 



6 



9 



6 



Temp., . 



42-0 



42-0 



47-4 



52-4 



54-5 



48-5 



44-3 



45-8 



45-7 



48-8 



55-3 



55-9 



49-9 



47-3 



44-8 



43-0 



43-0 



42-9 



Slope, 



+0-0 



+ 0-6 



+0-4 



+ 0-2 



o-o 



-0'2 



+ 0-3 



+ 0-1 



+0-7 



+2-3 



+ 0-0 



-0-1 



-o-i 



-o-i 



-0-4 



-0-1 



-0-4 







Depth, . 



44 



68 



34 



50 



65 



43 



49 



60 



44 



57 



48 



45 



49 



48 



64 



48 



62 



34 



Place, . 



S 



C 



D 



D 



C 



S 



S 



C 



S 



S 



C 



S 



S 



S 



C 



D 



S 



C 



The number of observations for each sounding is mentioned in the above table as 

 " No. of Pts." Temp, signifies the mean temperature of the vertical section in degrees 

 Fahrenheit. " Slope " is the range of temperature between the surface and bottom layer 

 of 5 fathoms thick. "When the surface is warmer, the slope is positive ; when the surface 

 is colder, negative. Depth is given in fathoms. 



The striking physical feature of the Channel is the tumultuous rush of the tides 

 (see Part I. p. 653). This appears, from the discussion both of salinity and of tempera- 

 ture, to effect a thorough mixing of the water from bottom to surface ; a condition 

 particularly well brought out by the curves of vertical distribution of temperature, which 

 are practically homothermic at all seasons of the year. Of the eighteen soundings in water 



