222 
BATHYMETKICAL SURVEY OF 
THE LOCHS OF ORKNEY. 
The Mainland of Orkney possesses many fine lochs. The land surface 
.consists of a series of low dark-topped hills, none reaching 1000 feet in 
height, between which are broad stretches of level or gently undulating 
moorland, now in great part under cultivation. In correspondence with 
this conformation of the land, and the absence of narrow valleys, the lochs 
occupying the hollows are all relatively broad, and they are without excep- 
tion shallow and flat-bottomed. The two very large bodies of water, the 
Lochs of Stenness and Harray, which ramify into the very heart of the 
island, are subject to the influence of the tides, though their level is but 
slightly affected. 
In the mountainous islands of Hoy and Rousay there are narrow valley 
lochs of greater depth than any on the Mainland. On the other islands of 
the group, which are quite low, there are only a few unimportant lochs, 
which were not surveyed. In the three islands visited (see Index Map, Fig. 
24) fourteen lochs were surveyed. The largest, in every respect, is the Loch 
of Harray ; the Loch of Stenness is little inferior in size, but all the others are 
much smaller. The deepest loch on the Mainland, the Loch of Stenness, 
17 feet in depth, is slightly exceeded in depth by the Muckle "Water in 
Rousay, but by far the deepest loch surveyed is the little Hoglinns Water 
in Hoy, which is 57 feet deep. The combined superficial areas of all the 
lochs surveyed amounts to 10 square miles, and the area draining into 
these lochs exceeds 90 square miles. 
The Island of Hoy is the most mountainous of the Orkneys. With the 
exception of the Peniusula of South Walls, joined to the main island 
merely by a causeway, the island consists of one mountainous mass, rising 
from south to north, where it culminates in three peaks of over 1300 feet 
in height, separated by deep glens which cut right across the island. The 
central peak, the Ward hill, 1564 feet in height, is the highest point in 
Orkney, and even exceeds the highest hill in Shetland (Ronas hill, 
1475 feet) by nearly 100 feet. On the southern slope of the island are 
several lochs, which, from their highland situation, might be expected to 
be deeper than the lochs in the plains of Pomona. That this is in fact the 
case can be definitely stated of one little loch, the Hoglinns Water, the 
survey of which, begun by the Lake Survey, was completed by Mr. William 
Marwick, who found a depth of 57 feet. The largest loch in Hoy, the 
Heldale Water, about a mile in length, was not surveyed. 
