750 DR E. M. WEDDERBURN AND MR A. W. YOUNG ON 



changed by as much as a third of a degree in the interval between successive pricks, 

 i.e. 4 minutes. 



2. Record at 10 metres for 24 hours commencing 19 h. 8 m. on 8th August. 

 About 4 hours after the beginning of this record there is a rapid rise in temperature 

 caused by the discontinuity passing across the 10-metre depth. It is seen that there 

 is a change of about 4° C. in an hour and a half. Although the change is not perfectly 

 uniform, there is little evidence of rapid movements such as would result from 

 boundary waves at the surface of discontinuity, and it must be assumed that none 

 such occurred in this instance. 



3. Record at 15 metres for 24 hours commencing 18 h. 21 m. on 9th August. 

 The rise in temperature shown about three hours after the beginning of the record 

 is probably due to an easterly wind depressing the isotherms at the west end of 

 the loch. 



4. Record for 24 hours commencing 18 h. 36 m. on 10th August. The first part 

 of this record was made at a depth of 15 metres, and shows a uniformity which is 

 markedly absent in the latter part of the record, when the instrument was raised to 

 10 metres, and was in the discontinuity layer. The presence of boundary waves is 

 well shown in this record. 



5. Record for 6 hours commencing at 12 h. 54 m. on 12th August. The first 

 part of this record was made at a depth of 10 metres. A train of boundary waves 

 has evidently occurred about 3 hours after the commencement of the observation, and 

 it is clear that the interval of 1 minute between successive pricks has been too long 

 to pick up all the variations. The last part of the record is taken at a depth of 

 13 metres. 



6. Record at 10 metres for 24 hours commencing at 16 h. 38 m. on 13th 

 August. This record shows very clearly the passage of the discontinuity past the 

 instrument, and there is distinct evidence of boundary waves in the upper part of the 

 layer of discontinuity with a period of about 11 minutes. The observations with 

 mercury thermometers for the same period are shown in fig. 8, and will be 

 explained later. 



7. Record at 10 metres for 24 hours commencing at 16 h. 40 m. on 15th August. 

 This record shows about 10 hours after the commencement the rise of the isotherms 

 past the instrument, and about 10 hours later their much more gradual fall, and the 

 usual embroideries are present. About 2 hours after the commencement there has 

 been a sharp drop in temperature, which may have been due to a solitary boundary 

 wave, or to a bore such as was described in the " Experimental Investigation of the 

 Temperature Changes occurring in Fresh-water Lochs," Proc. Roy. Soc. Edin., 

 vol. xxviii, p. 2. 



8. Record at 10 metres for 24 hours commencing at 17 h. m. on 17th August. 

 This record also shows an oscillation with a period of about 10 hours, and embroideries 

 with a period of about 25 minutes. 



