202 SALMONIA. 



its habits, and has remained there and mul- 

 tiplied. , 



HAL. There may be truth in what you 

 are now imagining, for the grayling requires 

 a number of circumstances in a river to en- 

 able it to increase. 



POIET. What circumstances are these ? 



HAL. A temperature in the water which 

 must be moderate neither two high nor too - 

 low. Grayling ai'e never found in streams 

 that run from glaciers at least near their 

 source ; and they are killed by cold or heat. 

 I once put some grayling from the Teme, in 

 September, with some trout, into a confined 

 water, rising from a spring in the yard at 

 Downton ; the grayling all died, but the trout 

 lived. And in the hot summer of 1825, great 

 numbers of large grayling died in the Avon, 

 below Ringwood, without doubt killed by the 

 heat in July. 



POIET. But I have heard of grayling 

 being common in Lapland at least so says 

 Linnaeus. 



HAL. I think it must be another species 

 of the same genus ; the same as Back's gray- 



