376 Proceedings of the Royal Society. 



Those marked and re-taken in 1841 were marked with hraa^ wire 

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

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

 gi-ilse 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 lb. was 

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

 the sea on the 10th of July, weig-hing 18 lb. Mr Young is of 

 opinion that salmon rather diminish than increase in size during 

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

 subject by numerous experiments and observations. 



2. On the Geology of Roxburghshire. 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, 

 first, to the stratified rocks ; secondly, to the igneous rocks ; and, 

 thirdly, 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 question regarding the 

 existence of the new-red sandstone formation in this county, Mr 

 Milne, whilst not wishing to affirm absolutely the non-existence of 

 any strata whatever belonging to this epoch, referred to the older for- 

 mation the great mass of the red sandstones abounding in the dis- 

 trict, adding that he had himself seen none which necessarily be- 

 longed to a later epoch. 



It was stated that no fossils had been found in the greywacke 

 strata, but that in the old red sandstone formation^ scales and bones 

 of the Holoptycliius had been found embedded both in the red and 

 the white coloured strata. 



The igneous rocks consist of all the varieties of felspars, basalts, 

 and greenstones, known in other parts of Scotland, the first men- 

 tioned of these being the oldest. All these rocks occur in the form 

 of dykes, as well as hills, of which the Eildons and Cheviots are the 

 highest and most extensive. 



