535 
Linlith- 
gowshire. 
Anas tadorna. 
Berwick- 
shire. 
0. 
Linlith- 
gowshire. 
Lams rissa. 
Berwick- 
shire. 
R. 
0. Podiceps minor. 
R. 
L. 
marinus. 
0. 
Uria troile. 
R. 
L. 
fuscus. 
0. 
U. grylle. 
R. 
L. 
argentatus. 
R. 
Alca torda. 
R. 
L. 
canus. 
R. 
A. artica. 
R. 
L. 
ridibundus. 
R. 
Peleeanus carbo. 
R. 
Sterna cantiaca. 
R. 
P. graculus. 
R. 
0. S. 
hirundo. 
R. 
P. bassanus. 
0. 
S. 
artica. 
R. 
Pufhnus anglorum. 
0. 
S. 
minuta. 
R. 
Procellaria pelagica. 
0. 
s. 
Dougalii. 
0. 
A pair of the grey shrikes named in the list, frequented some old 
thorn trees, near Torpliichen village, during the end of May and 
beginning of June 1846. 
The red-backed shrikes were observed by me in July 1859, at 
Oxendean, near Dunse Castle, Berwickshire. This, I believe, was 
the first time they have been seen in Scotland. The red-backed 
shrike passes the winter in Africa, and visits England in May. 
“ It breeds,” says Fleming, “ in the southern counties of Eng- 
land.” “It is,” says the late Bishop of Norwich, “generally 
speaking, very rare in most parts, confining itself to Essex, the 
Sussex Downs, Wiltshire, and Gloucestershire.” Mr Selby has not 
traced it farther north than Cumberland. M. E. T. Bennet, in one 
of his notes to White’s Selborne, refers to this bird as one which 
belongs to the south of England, and is scarcely ever met with in 
the north. In 1840, Mr M‘Gillivray recorded that “ it had not 
hitherto been observed in Scotland.” 
4. Note on Molecular Arrangement in Crystals. By 
Professor Tait. 
To illustrate my lectures on Molecular Forces, I sometimes use 
piles of marbles of equal size. Each of these is taken to represent 
the sphere of action of a symmetrical integrant molecule, in the sense 
that the attractive and repulsive forces necessary to a theory of 
molecules are balanced, when the distance of two molecules is equal 
to the diameter of the sphere. If the integrant molecules be not 
symmetrical, their spheres of action will be spheroids or ellipsoids. 
In arranging such piles, there are two obvious ways of construct- 
ing the layers, and two of applying layer to layer. 
4 c 
YOL. IV. 
