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 : — 
