14 Proceedings of the Royal Physical Society. 



lavas, during their molten and plastic condition, and were 

 no evidence of dressing. 



These plications are very curious, and exist only on the 

 top of domes, or blisters in the lava streams. They present 

 most beautiful curves, starting from the centre of the dome, 

 and often at the edges becoming straight and parallel, and, 

 when found broken up and separated from the tortuous por- 

 tions, might readily be mistaken for either slickensides or 

 glacial grooving. Below these plications, which are seldom 

 deeper than an inch, may be seen the rude basaltic form of 

 the lava arranging itself by shrinkage, by a slower cooling 

 process than the plicated surface above. Some idea may be 

 formed of the size of these blisters in the lavas, when I tell 

 you, that at Surtseller they are from 60 to 100 feet in dia- 

 meter. These blisters are mostly covered by the domes, 

 and as the horses' feet clatter over them, you can hear the 

 deep hollow sound echoed from below. One dome had fallen 

 in, and we gazed with awe and wonder down a cone as large 

 as any of those erected for the bottle-works at Leith. Its 

 interior surface had a most peculiar jagged appearance, 

 caused by the lava cooling in long drooping spikes. As at 

 Vesuvius, I could not find the slightest trace of a mineral 

 among the recent lavas, while the more ancient were filled 

 with zeolites and calcedony, another proof to me that a sub- 

 aqueous volcanic deposit (subsequently elevated) is the true 

 matrix of our simple minerals. 



In conclusion, allow me to congratulate you on the labours 

 of the last Session, and with the hope that, under the dis- 

 tinguished Presidents now in office, we shall be able, at the 

 conclusion of this Session, to present as goodly an array of 

 papers as we have had during the past. 



Dr M'Bain, seconded by Mr J. M. Mitchell, moved a vote 

 of thanks to Mr Bryson for his learned and interesting 

 address, and for his valuable services while president of the 

 Society. 



The motion was unanimously agreed to. 



The following Communications were then read : — 



