44 International Congress of Geologists. — Frazer. 
sedimentation and elevation under erosion, so common in 
every period of the earth's history. 
It would be a mistake however to suppose, as many do, 
that all crust oscillations are the result of weighting and 
lightening by sedimentation and erosion. There are un- 
doubtedly other causes, far more fundamental, determining 
these movements. Subsidence is often not the result but the 
cause of excessive sedimentation by continual renewal of the 
conditions of sedimentation ; and elevation is often the cause 
of excessive erosion by renewal of the conditions of erosion.^ 
That elevation is often produced by other causes be- 
sides lightening by erosion, is evident in cases of great 
lava-floods, where the crust is lifted by upswelling of 
the sub-crust liquid and broken by great fissures through 
which the sub-liquid is outpoured on the surface and the broken 
crust block readjusted by gravity in new positions. What is 
the cause of the intumescence of the sub-liquid in these cases, 
whether elastic force of steam incorporated in the magma by 
excess of water from above, or whether by hydrostatic pressure 
transferred from a subsiding area somewhere else, we do not 
know. 
THE LATE SESSION OF THE INTERNATIONAL CONGRESS 
OF GEOLOGISTS AT LONDON. 
By Persifor Frazer. 
Although several members of the late Congress took ample 
notes of the proceedings, no one has put his notes into the 
form of a permanent record in advance of the official volume, 
except Col. Joaquim Filippe da Encarnagao Delgado of 
the Portuguese engineer corps, director of the Geological Sur- 
vey of Portugal. 
There have been several causes for this ; one is that the dis- 
cussions at the London Congress settled very little if any 
thing, and barely if at all raised themselves above the com- 
monplace discussions in an ordinary meeting of a geological 
society. The Congress had no very important message for the 
world, and the world was not anxious to be informed of the 
business transacted by the Congress. 
Another reason may have been that those who were prepar- 
ed to give an account of the Congress were too busy to do so ; 
'' Amer. Jour., vol. 32, p. 180; 1886. 
