ADDITIONAL NOTES. 303 



indeed, the water of the Wye proved to be equally hard, if not 

 harder, and to contain a little sulphate of lime, which could not 

 be detected in the water of the Lathkil. The mean difference 

 appeared to me to be in the character of the several rivers, in 

 relation to volume, mode of flowing, and temperature ; the Wye 

 and Derwent being fuller and more constant streams, less liable 

 to be frozen in winter, and unduly heated in summer, streams, 

 in all respects, like these described by the author, as peculiarly 

 suitable to the grayling ; and further, from the nature of their 

 bottom, insuring a larger and more constant supply of that kind 

 of food, water-snails, Iarv89, squillse, &c., which the grayling a 

 fish needing good and plentiful food in whiter seems to require. 

 That the mere chemical nature of the water is not the main 

 cause of the unfitness of the Lathkil for grayling seems to be 

 shown by the circumstance that it enters the lower part of that 

 stream, and even breeds there a little above the junction with 

 the Wye, but does nob ascend beyond the first fall, a fall that 

 the trout readily passes, and which is not, I believe, higher than 

 some in the Wye and Derwent, that the grayling is known to 

 surmount. J. D. 



( Use of the Scales of the Eel, page 198.) 



Mention is made of the scales of the eel as likely to facili- 

 tate the progressive motion of this fish when out of water. 

 Considering the nature of these scales, doubt may be enter- 

 tained on this point. From an examination I have made of 

 them, I find they are commonly oval, about the 555th of an 

 inch in their long diameter, symmetrically arranged in com- 

 partments, approaching in form the oval. These may be seen 

 with a common magnifying-glass ; but to distinguish the scales 

 individually, a high magnifying power is required. Their form, 

 I may add, is best seen after a portion of the integuments has 

 been exposed to a charring or incinerating heat. In the latter 

 instance, when the charcoal is consumed their skeleton remains, 

 consisting of phosphate of lime, just perceptibly coloured by 

 peroxide of iron. Now, as these minute scales seem to be 

 adhering closely by their entire surface, and as the skin of the 

 animal is lubricated with viscid mucus, it is not obvious, nor 

 does it seem probable, that they can be of any service for loco- 

 motion in the manner supposed by the author. 



