158 Proceedings of the Royal Physical Society. 



conceivable that slow terrestrial tides may be set up within 

 the lithosphere under the conditions above referred to. It 

 was further pointed out that the variability in the downward 

 increment of heat observed when observations extending 

 over a large area are compared, may be easily explained if 

 the internal heat of the Earth is, even in part, due to one or 

 other of these auxiliary causes. 



XIII. On the Occuri^ence of the Lesser Whitethroat (Sylvia 

 curruca) iyi the Outer Hebrides, luith Memarhs on the 

 Species as a Scottish Bird. By William Eagle Clakke, 

 r.L.S., etc. 



(Read 15tli February 1899.) 



Scottish specimens of the Lesser Whitethroat are rarm 

 aves. The one exhibited at this meeting was obtained on 

 the island of Barra, one of the southernmost of the Outer 

 Hebrides, on the 24th of October last, and has been sub- 

 mitted to me for determination by its captor, Mr W. L. 

 Macgillivray, a nephew of the distinguished ornithologist of 

 that name. 



This bird was shot on the west side of the island, and is 

 the first known to have been obtained in, or about which we 

 have any reliable information for, the Western Isles. That 

 it was blown out of its course, or lost its way during its 

 migration southwards, is the probable explanation of the 

 appearance of this waif so far to the west ; and in this con- 

 nection it is of interest to remark that Mr Macgillivray sent 

 along with it a Garden Warbler {Sylvia hortensis), captured 

 on the same day — the second known occurrence of this 

 species in the Outer Hebrides. 



This Hebridean example of the Lesser Whitethroat is in 

 adult plumage, and has been presented by Mr Macgillivray 

 to the fine collection of British birds in the Museum of 

 Science and Art, Edinburgh. 



I desire to take this opportunity of calling attention to 

 the very unsatisfactory statements made in all the modern 

 standard works on British birds, to the effect that the Lesser 



