NATUUAL HISTOUY OF SELBOENE 
183 
apparently turn them forward or backward in their sockets as occasions 
require. They take little notice of a lighted candle, though applied 
close to their heads, but flounce and seem much frightened by a sudden 
stroke of the hand against the support whereon the bowl is hung ; 
especially when they have been motionless, and are perhaps asleep. As 
fishes have no eye-lids, it is not easy to discern when they are sleeping 
or not, because their eyes are always open. 
Nothing can be more amusing than a glass bowl containing such 
fishes ; the double refractions of the glass and water represent them, 
when moving, in a shifting and changeable variety of dimensions, 
shades, and colours ; while the two mediums, assisted by the concavo- 
convex shape of the vessel, magnify and distort them vastly ; not to 
mention that the introduction of another element and its inhabitants 
into our parlours engages the fancy in a very agreeable manner. 
Gold and silver fishes, though originally native of China and Japan, 
yet are become so well reconciled to our climate as to thrive and 
multiply very fast in our ponds and stews. Linnaeus ranks this species 
of fish, under the genus of Cyprinus, or carp, and calls it Cyprinus 
auratus. 
Some people exhibit this sort of fish in a very fanciful way ; for they 
cause a glass bowl to be blown with a large hollow space within, that 
does not communicate with it. In this cavity they put a bird occa- 
sionally ; so that you may see a goldfinch or a linnet hopping as it were 
in the midst of the water, and the fishes swimming in a circle round it. 
The simple exhibition of the fishes is agreeable and pleasant ; but in 
so complicated a way becomes whimsical and unnatural, and liable to 
the objection due to him, 
" Qui variare cupit rem prodigialit^r unam. " 
I am, &c. 
LETTEE LY. 
TO THE SAME. 
October im, 1781. 
Dear Sir, — I think I have observed before that much of the most 
considerable part of the house-martins withdraw from hence about the 
first week in October ; but that some, the latter broods I am now con- 
vinced, linger on till towards the middle of that moiith ; and that at 
times, once perhaps in two or three years, a flight, for one day only, has 
shown itself in the first week in November. 
Having taken notice, in October, 1780, that the last flight was 
numerous, amounting perhaps to one hundred and fifty ; and that 
the season was soft and still ; I was resolved to pay uncommon attention 
to these late birds; to find, if possible, where they roosted, and to 
determine the precise time of their retreat. The mode of life of these 
latter Hirundines is very favourable to such a design ; for they spend 
the whole day in the sheltered district, between me and the Hanger, 
sailing about in a placid, easy manner, and feasting on those insects 
