CLYDE SEA AREA. 



61 



itself: if the isotherms indicate a shearing movement in the water, the only efficient cause 

 seems to be the tidal current, which at the beginning of flood may have carried warmer 

 surface water along the west side, but this would not account for the westward dip of the 

 deepest isothermal sheets. 



The larger seasonal effects, as shown at the Skate Island station, may be best brought 

 out by grouping the curves of each year so as to show the stage of heating and cooling- 

 arrived at at certain definite dates as equally spaced as possible. For this purpose it 

 would be very important to have curves smoothed by taking the average of two at a 

 short interval apart, but this is only possible in the cases cited above. Where exact 

 averages cannot be obtained, the curves may sometimes be smoothed, in a manner 

 not altogether arbitrary, by combining neighbouring observations, and when this is done 

 the fact will be mentioned in the description. 



Figures 13 to 15 on Plate VII. show the results for the three seasons, corresponding- 

 curves being similarly coloured. The dates to which the various curves correspond are 

 as follows : — 



Table XX. — Typical Vertical Temperature Carves off Skate Island. 



Curve. 



Type. 



1886-87. 



1887-88. 



1888. 

























No. in 



Mean 



Time 



No. in 



Mean 



Time 



No. in 



Mean 



Time 







Table XIX. 



Date. 



Interval. 



Table XIX. 



Date. 



Interval. 



Table XIX. 



Date. 



Interval. 



I 



Minimal, . 



6 



27 March 



[ 23 days 



} 63 ,, 



|7»„ 

 i 



15 



28 March 





31 



22 March 



1 39 days 















[ 43 days 







II 



Early Heating, . 



7 



19 April 





10 May 



} 37 „ 



Mean 33, 34 



30 April 











16 









36 ,, 



III 



Rapid Heating, 



8 



21 June 



Mean 17, 18 



16 June 



35 



5 June 



! 















80 „ 







) 



IV 



Maximal, . 



Mean 9, 10,11 



7 Sept. 



„ 23, 25 



4 Sept. 



1 



f 112 „ 







U36 „ 



V 



Early Cooling, . 



12 



16 Nov. 



j 70 „ 







36 



19 Oct. 



1 











43 „ 







) 









VI 



Later Cooling, . 



13 



29 Dec. 



} 40 ,, 



,, 26, 27 



25 Dec. 





















59 „ 









VII 



Final Cooling, . 



14 



7 Feb. 



,, 29, 30 



21 Feb. 



) 









The correspondence in date is not very close, but all the curves having the same 

 number show a similar form, and belong to the same type. The first year is the most 

 characteristic, and may be taken as generally typical of the order of temperature changes 

 at this station. While the forms of the curves in different years are substantially the 

 same, the position in temperature varies considerably. To some extent, this may be 

 explained by the want of an observation at the actual date of maximum or minimum, 

 but there is also a difference due to the different thermal amplitude of each season. 



The critical points, where one curve changes into another, are described in some detail 

 for Garroch Head ; see figs. 12 to 15, Plates XXIV. and XXV. The minimum in each case 

 is typically homothermic, and No. 2, the curve of early heating, is derived from it by a 

 scarcely perceptible or quite imperceptible change in the lower layers, but a marked positive 



