Natural History. — Zoology. 225 
20. Structure of Crystals.— Recent investigations having 
directed the attention of observers in a particular manner to 
the study of the optical characters of crystallised minerals, we 
think it may not be without use to notice a circumstance in the 
structure of crystals, which, if not known, or neglected, may 
lead into error. Many crystals, which, in a general view, ap- 
pear simple, are found to be compound, when all their rela- 
tions are attended to ; and these, when examined optically, 
will present a compound in place of a simple structure. The 
simple structure characterises the Species of minerals, while the 
compound structure often distinguishes the Variety or subspe- 
cies. 
ZOOLOGY. 
21. Notices relating to the Nightingale. — u The nightingale,' 
(Motacilla luscinia,) so justly famed for its enchanting song, 
does not visit this northern part of England so frequently as 
it did forty or fifty years ago ; this is a fact agreed upon by 
all persons , to whom I have made application on the subject, 
and who have noticed the arrival, and other particulars re- 
lative to this bird. Whatever may be the cause, it is con- 
fessedly seldom heard in this part of the island. I well re- 
collect going, about eighteen years ago, when I was a boy, 
to a small coppice at a short distance from my paternal roof, 
to listen to the dulcet notes of this nightly warbler : — 
from that time to the present year I had never heard it, 
till the 9th June last, in the evening of which day it was 
heard, at a short distance from my residence ; and for several 
successive evenings, I heard it even before retiring to rest, or, as 
I reposed on my bed, I believe at every intermediate hour from 
eleven to three. I strongly suspected its nest was in a small 
thicket, composed of hawthorn, laburnum and filbert bushes, 
situated at one end of my garden, as I often saw the bird 
there, particularly in the evenings about sunset, when it began 
Some slight chirping, but retired generally to the NE. by E., 
to a thick and high hawthorn hedge, and Occasionally to NW., 1 
£>r near that point, in the same hedge where it always sung. 
The two diverging lines from the thicket to its station, forming 
VOL. v. no. 9- JULY 1821. r 
