NATURAL HISTORY OF SELBOKNE. 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 rena prodigialitfer unam." 



I am, &c. 



LETTEE LY. 



TO THE SAME. 



October 10th, 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 month ; 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 



