[ 1 5 7 3 
bounding the Eddy, makes that Part of the Sea 
rougher in blowing Weather, and of a darker Colour 
in Calms, than the reft, by which the Limirs and Di- 
rection of thefe Eddies are always diltinguifhe'd. 
The Colliiion of the oppofite and oblique Streams, 
near the Ends of the Illand, will excite a circular 
Motion in the Water, and, if the Celerity of the 
Tide is confidcrable, will occahon Whirlpools, or 
Cavities in the Sea, in Form of an inverted Bell, 
wide at the Mouth, or at the Surface of the Sea, and 
growing gradually narrower toward the Bottom : 
Their Width and Depth are in proportion to the 
Rapidity of the Streams that caufe them, and are 
fometimes fo large as to be dangerous. Thofe in 
Zetland Firth , near the Iilands Stroma and Swona , 
may, with Spring-Tide, turn any Velfel quite round, 
but are never fo large as to endanger one otherways: 
There have been Inftances, however, of Email Boats 
dropping into, and being fwallowed up by them. The 
Hiatus , or Cavity, is largeft when it is hrft formed, 
and is carried along with the Stream, diminishing 
gradually in Dimenlions as it goes, until it quite dilap- 
pears. The Su&ion, or fpiral Motion communicated 
to the Water, does not feem to extend far beyond the 
Hiatus. 1 paffed, in a Boat, within 20 Yards of 
one, without being fenfible of any Attraction 5 but 
indeed it was toward the latter End of the Tide, 
when its Strength was much abated : The Diameter 
of the Cavity, at that time, I judged to be between 
two and three Feet. When Fifhermen are aware of 
their Approach toward a Whirlpool, or Well, as it 
is called in Orkney , and have Time to throw an 
Oar, or any other bulky Body into it before they 
are 
