*8 



DR HUGH ROBERT MILL ON THE 



the Plateau, about Ailsa Craig, very small. But on the run from Lamlash to Campbel- 

 town, which was frequently made, observations were secured pretty often across the 

 northern end. The common observing places were (1) to the south-east of Pladda, (2) 

 midway between Pladda and Sanda, and (3) to the east or north-east of Sanda. Some- 

 times no observations could be made beyond the shelter of the land, and then they were 

 usually carried out off Rhuad Point or Davaar Island, near the Cantyre coast, or off 

 Bennan Head, in the south of Arran. 



The observations may be grouped for convenience into an eastern and a western set, 

 but the locality of each sounding is in each case indicated. Observations made by the 

 Fishery Board's cruiser "Vigilant," and discussed by Mr Herbertson and myself in the 

 Eleventh Annual Report of the Fishery Board for Scotland, furnished some data contem- 

 porary with those of the " Medusa," and supplementary to them. 



Table VII. gives particulars of dates and mean temperatures at stations on the east 

 and south-east parts of the Plateau. 



Table VII. — Observations on the Great Plateau (Eastern Side). 



No. 



1 



2 



3 



4 



5 



6 



7 



8 



9 



10 



11* 



12 



13 



14* 



15* 



16* 



17* 



Date. . . . 



20.6.86 



22.9.86 



26.12.86 



5.5.87 



17.6.87 



6.7.87 



21.9.87 



21.9.87 



21.9.87 



21.9.87 



1.10.87 



10.12.87 



19.1.88 



14.2.88 



17.2.88 



26.4.88 



9.5.88 



No. of Points 



5 



7 



4 



13 



9 



13 



7 



7 



4 



4 



6 



6 



6 



5 



5 



6 



6 



Temperature 



48-8 



54-0 



46-3 



45-3 



49-8 



51-5 



55-2 



55-6 



55-3 



557 



53-7 



47-7 



45-3 



44-4 



44-3 



43-7 



44-5 



Slope . . . 



+ 5-3 



-0-8 



+ 0-1 



+ 1-4 

 ( + -ll) 



+ 4-8 



+ 8-9 



o-o 



(til) 



o-o 



0-1 



-01 



+ 0-5 



o-o 



-0-6 



-1-4 



-1-7 



+ 0-8 



+ 2-1 



Place. . . . 



P 



A 



P 



A-P 



P 



P 



A-P 



A-P 



A 



A-S 



P 



P-S 



A 



P 



P-A 



A.-S 



A 



Depth . . . 



20 



26 



11 



29 



25 



23 



30 



28 



32 



28 



22 



23 



36 



30 



30 



28 



25 



* "Vigilant " Observations. 

 P, east or south of Pladda. A, near Ailsa. A-P, between Ailsa and Pladda. A-S, between Ailsa and Sanda. 



With so few data, scattered so irregularly over a long interval of time, it would be 

 useless to attempt detailed discussion ; but the general average rate of heating and cool- 

 ing of the mass of water may be deduced as in Table VIII., — the wide flat expanse of the 

 Plateau allowing one to assume the mean vertical temperature of the station as approxi- 

 mately that of the whole q uantity of water in the neighbourhood. 



Table VIII. — Rate of Change of Water- Temperature on the Great Plateau (Eastern Side). 





Period. 



Temperature 

 Change. 



Days. 



Mean rate of 

 Change per Day. 



Remarks. 



1886 

 1887 



1888 



June 20-September 22 

 September 22-December It 



June 17-September 21 

 September 21-October 1 

 October 1-December 10 . 

 December 10-January 19 

 January 19-February 14 



April 26-May 9 . . . . 











+5-2 

 -7-7 



+ 4-5 

 + 5-6 

 -1-5 

 -4-0 

 -2-4 

 -0-9 

 -07 

 + 0-8 



94 

 95 



33 

 96 

 10 

 71 

 40 

 26 

 71 

 13 



+ °'°55 

 — o - o8r 



+ 0-136 

 +0-058 

 -0-150 

 -0-056 

 -o - o6o 

 -°"°35 



-O"0IO 



+ o - o6i 



Valueless through lost minimum. 

 Probably includes minimum. 



