CLYDE SEA AEEA. 3 



of the annual minimum, when the temperature appears to become uniform both in regional 

 and bathymetrical distribution. At other times, however, it was only found possible to 

 estimate the heat-content of the water in small and well-defined natural regions. 



In presenting this paper, I have to express my thanks to many, friends and fellow- 

 workers for advice and assistance. Dr John Murray, who initiated and directed the 

 whole work, has, at various stages, given the most helpful suggestions, and the observa- 

 tions made in the later trips of the "Medusa" were done entirely under his supervision 

 or by himself personally. Mr J. Y. Buchanan, F.R.S., kindly gave the use of his 

 observations on Loch Lomond, for comparison with those on the lochs of the Clyde 

 Sea Area. Mr A. J. Herbertson and Mr E. Turnbull drew all the curves of vertical 

 distribution of temperature for each station ; Dr W. Peddie estimated the mean 

 temperature of each of the curves ; while Mr H. N. Dickson estimated the mean 

 temperature of the various loch-basins from the vertical sections, and rendered other 

 help. 



Instruments and Methods. 



Surface Temperature. — The temperature of the surface water was observed in 

 two different ways, which gave practically identical results. When a serial temperature- 

 sounding was made, the Negretti and Zambra reversing thermometer was employed, the 

 frame of the instrument being just immersed, so that the bulb was about six inches below 

 the surface. On other occasions, when it was desirable to obtain the surface temperature 

 without stopping the vessel, a bucketful of surface water was taken on board, and a 

 mercurial thermometer, with large bulb and stem divided into degrees Fahrenheit, 

 immersed in it. The bucket was placed in the shade, and the thermometer left in 

 it for about two minutes, being used to stir the water thoroughly before it was 

 read. Care was always taken to draw the sample of water well forward in the vessel, 

 so that there could be no possibility of admixture of warm water from the condenser 

 or any discharge-pipe. The error of the surface thermometer was carefully ascertained, 

 at intervals of a few months, by comparison with a standard thermometer. 



Deep-Sea Thermometer. — For observations beneath the surface the instrument exclu- 

 sively employed was Negretti and Zambra's Patent Standard Deep-Sea Thermometer. 

 All thermometers used were graduated on the Fahrenheit scale, which presents many 

 advantages for observational purposes, and all temperatures are given on that scale. The 

 principle of the thermometer is well known. It is in fact an out-flow thermometer, in 

 which the mercury that escapes from the bulb is measured instead of being weighed. 

 There is a constriction in the stem just above the bulb, and then the bore is enlarged into 

 a small lateral pouch or chamber. In an upright position the thermometer acts like any 

 other, but when it is inverted the mercury column breaks off at the constriction and runs 

 into the tube, which is graduated in degrees so as to be read in the inverted position. 

 The whole thermometer is sealed up in a strong glass tube to protect it against pressure, 

 and the bulb is surrounded with mercury to transmit the heat rapidly. 



After the thermometer is inverted, the record of the temperature remains unchanged, 



