Transactions. 251 



for the most part bright and suuny, or if cloudy or rainy, very 

 mild, with south or south-west winds. 



I have also to submit a table shewing the mean monthly 

 temperatures of the air and water of the estuary of the Nith at 

 Kingholm Quay, and taken with great regularity by Mr James 

 Lewis, for a period of about nine months, from 25th June, 1889, to 

 21st March, 1890. The hours of observation necessarily varied, 

 because the proper temperature of the estuary could be obtained 

 only when the tide was up. For the most part they were taken 

 between the hours of 9 a.m. and 4 P.M., though sometimes a little 

 eailier and sometimes a little later. 



From 25th June to 31st July 



,, 1st to 31st August 



„ 1st to 30th September 



,, 1st to 31st October 



„ 1st to 30th November 



,, 1st to 14th December 



,, 1st to 31st January 



„ 1st to 28th February 



„ 1st to 21st March 



Sums 



Means 



From this table it will be seen that for the period from 25th June 

 to 31st July the mean temperature of the estuary was a fraction of 

 a degree higher than that of the air, and the same thing occurred 

 again in October. In all the other months it was lower, but 

 not to the same extent as in the case of the river temperature. 

 Taking the whole period during which observations have been 

 made, the mean temperature of the air was 47-7'' and of the water 

 46°, giving a mean difference of only 1-7°, instead of 4-3=' as in the 

 case of the river. This result might have been somewhat modified 

 if the observations had been extended over the whole year instead 

 of nine months, but not, I think, to any great extent, there being 

 an obvious reason why the temperature of the estuary should be 

 higher than that of the river as compared with that of the air, viz., 

 the fact that when the tide rises it passes over the extensive tracts 

 of sand which in the Sol way Firth are left bare by the receding 

 tide, and in sunny days become heated by the sun, to which it 

 may be added that the influence of the Gulf Stream must tell in 



