2 DR HUGH ROBERT MILL ON THE 



memoir is, in large measure, a patchwork or agglomeration of minor discussions, the 

 result of the attempt to do a piece of original work in physical geography in a country 

 where there is scant recognition in the Universities of such special study or research. 

 I must, however, record my indebtedness to the temporary Elective Fellowship in 

 Experimental Physics in the University of Edinburgh, which enabled me to devote two 

 years exclusively to the practical work of carrying out observations, and to the 

 Government Grant Committee for sums of money which sufficed to pay for such 

 additional assistance as" was required in carrying out the discussion. Without such help, 

 the work would have been impossible. Any value it now possesses lies in the fact 

 that it is a presentation of actual observations made at the same stations, with the 

 utmost care, and by precisely the same methods, although at somewhat irregular 

 intervals of time, for three and a half years. These observations were published partly 

 in the Journal of the Scottish Meteorological Society * and partly in the Proceedings 

 of this Society. t Here they are arranged in the manner which, after repeated trials, 

 seems to be that best adapted to bring out their characteristic features: in some 

 aspects they are generalised, and in every case, as far as possible, brought into 

 connection with the related tidal or climatic phenomena. 



One of the most instructive results is that the omission of one or two sets of observa- 

 tions would give an entirely different complexion to the whole series. Not only might 

 the date of a seasonal maximum or minimum be missed in this way, but the sudden and 

 profound disturbances of seasonal changes, which are otherwise apparently uniform, 

 would pass undetected. These irregular changes make it doubtful whether any one year 

 can be fairly compared with any other. The determining conditions of temperature-change 

 are much more numerous and complicated than was suspected from the preliminary 

 discussions made while the observations were in progress.^ Thus it now appears 

 that it is necessary to know the direction and force of the wind, not only at the 

 time when the observations were made, but every day during the whole period of 

 observation. And since the direction of the wind is modified by the configuration 

 of the land around each loch, it is impossible to arrive at the actual directions from 

 a study of the weather-charts. There are practically no meteorological stations in 

 the landward division of the Area, so that no contemporary observations of wind are 

 available. These limitations have been carefully kept in view, and I have endeavoured 

 to carry each train of reasoning no farther than is justified by the ascertained facts. 



It was originally my ambition to calculate out the total changes of heat for the 

 whole Clyde Sea Area looked upon as a closed system ; but after working long at the 

 problem I was obliged to abandon it on account of the small number of observations in 

 the seaward part, and the unknown influence of the wide margin of shallow water along the 

 Ayrshire coast. A fairly good guess may be made of the total amount of heat at the time 



• Journ. Scot. Met. Soc, 3rd ser. (1886), vol. vii., No. 3, pp. 313-351 (1887), vol. viii., No. 4, pp. 47-110. 



+ I'roc. Rmj. Soc. Edin., vol. xviii., pp. 139-228. 



t Physical Conditions of the Water in the Clyde Sea Area, Proc. Glasgow Phil. Soc, vol. xviii. (1887), pp. 332-356. 



