of Edinburgh, Session 1885 - 86 . 
417 
14 th November . — It had been raining all night, but cleared when. 
I arrived at Balloch. 1 was accompanied by Mr Morrison, from the 
Scottish Marine Station at Granton, who brought with him three 
overturning thermometers. A very heavy snow squall occurred on 
the way up the loch, but it cleared off before we arrived at Inver- 
snaid. While at Inversnaid the weather was very favourable, and 
we had no difficulty in getting this series of observations. The 
temperatures at 65, 85, and 100 fathoms were taken with my 
thermometers, the others were taken with the overturning thermo- 
meters of the IST egretti type. In the afternoon a series of tempera- 
tures was taken with the overturning thermometers in the Luss 
basin west of the Ross Islands. 
The salient feature at both stations is the great cooling which has 
taken place since 15th October. The whole body of water in the 
Luss basin has been cooled 2J°. The temperature of the bottom 
water at Inversnaid has risen 0°*1, and it has probably reached its 
maximum. 
Having described and discussed the observations made at the 
different stations at the same date, it will be useful to consider some 
of the stations with respect to the variation in the distribution of 
temperature with changing season, and for this purpose it will be 
convenient to take two typical stations, namely, that at Ross Mill in 
the Luss basin, w r hich represents a shallow lake, and that at Inver- 
snaid, representing a deep one. 
The Luss Basin . — Observations were made in this basin on 5th 
September, 22nd September, 15th October, and 14th November. 
Already on the 5th September the curve has almost lost its 
summer feature, and is becoming pronouncedly autumnal. On 
15th October it has assumed the winter form, and between that 
date and 14 th November the nearly uniform temperature of the 
water has fallen about 2 0, 6 F. The surface temperature falls 
from 55°*2 on 5th September to 53°*6 on 22nd September, to 49°*4 
on 15th October, and 46° *6 on 14th November. The autumnal 
zone of nearly uniform temperature in the surface layer extends on 
6th September to 15 fathoms, and on 15th October to the bottom. 
Therefore, until some date between the 22nd September and 15th 
October the upper stratum of water is being cooled on both sides — 
that is, it loses heat by radiation and convection upwards into the 
VOL. XIII. 2 F 
