399 



grilse increase in size, those being the largest which abide the longest 

 in the sea. They spawn in the rivers after their first ascent, and 

 before they have become adult salmon. 



Mr Young also described various experiments instituted with the 

 view of shewing the transition of grilse into salmon. He marked 

 many small grilse after they had spawned in winter, and were about 

 to re-descend into the sea. He re-captured them in the course of 

 the ensuing' summer as finely-formed salmon, i-anging in weight from 

 9 to 14 lbs., the difference still depending on the length of their 

 sojourn in the sea. He has tried these experiments for many sea- 

 sons, but never twice with the same mark. A specimen marked as 

 a grilse of 4 lbs. in January 1842, and re-captured as a salmon of 

 9 lbs. in July, was exhibited to the Society. It bore a peculiarly 

 twisted piece of copper wire in the upper lobe of the caudal fin. 

 Those marked and retaken in 1841 were marked with brass wire 

 in the dorsal fin. With these and other precautions Mr Young 

 avoided the possibility of any mistake as to the lapse of time. Both 

 grilse and salmon return uniformly to their native streams ; at least 

 it very rarely happens that a fish bearing a particular mark is found 

 except in the river where it was so marked. Salmon in the perfect 

 state as to form and aspect, also increase rapidly in their dimensions 

 on again reaching the sea. A spawned salmon weighing 12 lbs. was 

 marked on the 4th of March, and was re-captured on its return from 

 the sea on the 10th of July, weighing 18 lbs. Mr Young is of 

 opinion that salmon rather diminish than increase in size during 

 their sojourn in rivers ; and he illustrates this and other points of his 

 subject by numerous experiments and observations. 



2. On the Geology of Roxburghshire. Part 2. By David 

 Milne, Esq. 



Mr Milne divided his paper into two parts, the first comprehending 

 a description of the leading geological features of the district ; the 

 second containing the inferences of a cosmological character, which 

 the facts related in the first part seemed to warrant. 



In describing the geology of Roxburghshire, Mr Milne referred, 

 Jirst, to the stratified rocks ; sccondli/, to the igneous rocks ; and, 

 thirdli/, to the superficial, or (as they have been sometimes termed) the 

 diluvial deposits. 



The stratified rocks were stated to consist of the following series, 

 beginning with the oldest, viz. — greywacke, old red sandstone, and 

 the coal measures. As to the long disputed ipestion regarding the 



