

ARK AN. METEOROLOGY. 327 



could not have been effected by the position of the land ; 

 certainly at least not by its mechanical interposition. But 

 the complicated nature of atmospheric currents has been 

 hitherto but little investigated and ill understood : it is one 

 of the many unexplained points in meteorology which 

 must be left for future investigation. As the subject 

 however is interesting, I shall add to this instance some 

 other remarkable examples of a parallel nature which 

 occurred during the investigation of the Western islands. 

 They all present cases of partial winds, which are well 

 known to mariners, but have not experienced that atten- 

 tion from philosophers which their singularity merits. 

 They do not appear to admit of explanation by any theory 

 that has yet been proposed, and are evidently independent 

 of differences of temperature, or of any differences of 

 gravity or density in adjoining portions of the atmosphere. 



The rising of sudden and local squalls in a tranquil 

 atmosphere, is one of these phenomena, which may be 

 experienced in great perfection in most of the sea lochs 

 of the western coast, and is, in particular, frequent and 

 violent in the deepest and most mountainous ; as in Loch 

 Hourn, and still more, in Loch Scavig. When the whole 

 atmosphere appears at rest, and the sea is like a mirror, a 

 gust of wind will descend with a rapidity and suddenness 

 resembling the blow of a hammer ; often momentary, and 

 rarely blowing for more than a few minutes in one direc- 

 tion. The navigation of these lochs becomes thus ex- 

 tremely dangerous, particularly to boats; while even 

 vessels of large size are sometimes brought in an instant to 

 their beam ends. At Fort William these squalls some- 

 times emulate the effects of a West India hurricane; 

 sloops having been blown up dry on shore ; while it is not 

 unusual hi these situations to see boats on the beaches 

 carried away by the wind and broken to pieces. 



The following presents a remarkable instance of the 

 permanent and partial currents which are so frequent on 

 this coast, as they are in similar situations elsewhere. 



