INTRODUCTION 
17 
This electroscope consists of a copper cylinder, containing a brass 
conductor, insulated by being supported on a quartz rod, and having 
at its upper end a slight brass rod, carrying a gold leaf, the deflection 
of which indicated the leak of the electrical charge. The experiments 
showed that, by surrounding the electroscope-case with a layer of 
water 120 feet thick, the conductivity, and therefore the ionisation, 
of the contained air is reduced, but not to less than 75 per cent, of 
the value which it has when the instrument is standing on dry land. 
Seiches. — The first authentic seiche recorded in Scotland was 
observed by members of the Lake Survey staff' in May 1902, while 
sounding Loch Treig, the amplitude being measured by placing a 
foot-rule in the water. A Sarasin limnograph was purchased in 1902, 
and set up at Fort Augustus, on Loch Ness, in June 1903. A second 
Sarasin limnograph was purchased in 1904; while in 1905 Professor 
Chrystal introduced several modifications, and had an improved 
form of the instrument constructed for use on Loch Earn. A 
statoscope was also employed by Professor Chrystal in connection 
with his seiche work, as well as barographs and sensitive barographs. 
These instruments are described in Professor ChrystaPs article 
forming part of this volume. 
Transparency. — Systematic observations on the depth at which 
discs of various colours disappeared from view when innnersed in the 
waters of Loch Ness were made in July, August, October, November, 
and December 1903, and January 1904. This depth for white discs 
varied from 14 feet on 27th August, after heavy rain during the 
night, to 24 feet on 4th August. On 27th October a white disc 
was visible to 16 feet, a yellow disc to 15 feet, and a blue disc to 
12 feet. The yellow disc could not be distinguished from the white 
disc so soon as it had descended about a foot, and the blue disc 
appeared quite green at that depth. 
Similar experiments were made in other lochs, but it was found 
that the transparency of the water varied so much, according as the 
rivers were in flood, and according to the development of the plankton, 
that these observations were continued only when local circumstances 
made it desirable. 
Currents. — In his recent work on Loch Garry and Loch Ness, 
Mr Wedderburn has made use of an Ekman current meter. 
Biological Observations. — On one occasion, the Mermaid, the 
steamer belonging to the Marine Biological Association of the West 
of Scotland, was hired for several weeks, and, being specially fitted 
for trawling and dredging operations, a minute exploration of the 
deep waters of Loch Lochy and Loch Ness was possible. The other 
lochs w^ere explored from rowing-boats or small steam launches with 
the usual nets and dredges in use among naturalists, such as tow-nets 
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