99 
1908-9.] Temperature Observations in Loch Garry. 
which was used in Loch Ness, so that a continuous record of the tempera- 
ture in the deepest part of the lake could be obtained. The Callendar 
Recorder was set up on the southern shore of the lake opposite the deepest 
part, but great difficulties were experienced with the platinum thermometer 
and the cable. The thermometer had been designed to stand a pressure of 
300 feet of water, but it was found that the pressure at a depth of 200 feet 
was too much for it. A new covering was procured for the thermometer, 
but after that, it was found that the insulation of the cable, which was the 
one used on Loch Ness, had become very faulty, and the use of the Callendar 
Recorder had finally to be given up without any trustworthy records being 
obtained, and mercury thermometers had to be relied on for all observations. 
Observations by means of mercury thermometers were carried on every 
day so far as weather and circumstances permitted. Readings of the air 
Fig. 1.— Macdonald’s Messenger. 
temperature were made by a maximum and minimum thermometer (un- 
screened) placed on the shore of the loch. A buoy was moored over the 
deepest part of the loch, and most of the observations were made from a 
boat attached to this buoy. A light anchor was also carried in the boat, 
and by means of it the boat could be readily anchored at any part of the 
loch. In this way one person was able to make the observations, save in 
very stormy weather. 
The ordinary reversing mercury thermometer was used with a messenger 
designed by Macdonald, which proved admirable. The usual dividing 
messengers are troublesome to use in cold weather, as one or both of the 
parts is very liable to get lost owing to the numbness of the observer’s 
hands while working in cold water. Macdonald’s messenger was formed by 
twisting a bar of metal into a spiral which could then be screwed on to the 
sounding line without much fear of losing it. The construction of the 
messenger sufficiently appears from the photograph which forms fig. 1 * 
* For a description of methods of thermometry, see Dr H. R. Mill’s “Clyde Sea Area,” 
part iii. and plate i., Tro.ns. R.S.E., vol. xxxviii. p 3. 
