Dr. G. Baur—On Scaphognathus, Newton. 171 
portion of the interior mass as would be equivalent to the increased 
size caused by the heat supplied to the later formed strata. In- 
dependently of this, the calculations deduced from the expansion of 
rocks by heat, as determined by the experiments of Bartlett, Adie 
and Mellard Reade, indicate that when exposed to high degrees of 
temperature, the enlargement is not sufficient to induce more than 
a fractional part of what is attributed to it. 
Hlevation of land does not eccur where the greatest amount of 
accumulation is in progress; on the contrary at the mouths of great 
rivers, where simultaneously with, or rather, as is here contended, 
in consequence of the immense accretion of sediments derived from 
the erosion of the land, and brought down and deposited, subsidence 
has been proved to have taken place to a very great extent, forming 
conditions such as it is considered by most would render the deeply 
buried strata liable to be exposed to an increase of heat supplied from 
below. It is in those areas where the greatest amount of denudation 
has taken place, and the land has become lightened in the process 
of removal, that elevation occurs. 
It is evident that where foldings occur, in what may be designated 
unaltered strata, they have been formed at the sea-level or at some 
moderate depth ; if in those in which extensive chemical change has 
produced a re-arrangement in their constituent components, they 
have been buried beneath a very thick covering of strata, which has 
enabled them to become affected by internal heat. However high 
they may subsequently have become elevated, this pre-supposes the 
removal of this immense quantity of material before the metamorphic 
rock became exposed at the surface, and formed a portion of the 
structure of mountains. 
From the examination of the geological structure of Britain it is 
seen that the erosion of these hard rocks, and their formation into 
hills and valleys, during a former period, though they may have sub- 
sequently sunk below the then sea-level, and been deeply buried 
beneath large accumulations of sediment, have still had a great effect 
in determining the present contour of the land. The flanks of buried 
valleys and the summits of ancient hills again become elevated and 
exposed by the removal of the less consolidated strata; the hardness 
and indestructibility which preserved them before, again enables 
them to stand conspicuous at a higher altitude than later deposits, 
and to form what has been called “the core of the mountain”; even 
the old valleys sometimes again serve the purpose by and for which 
they were originally formed; and streams run in them in the same 
course, often in the identical old channels. 
VI.—Mr. E. T. Newron on PreRosavrgia. 
By Dr. G. Baur, New Haven, Conn. 
Vee paper by Mr. E. T. Newton! “ On the Skull of Scaphognathus ” 
is one of the most important contributions to the morphology of 
1 Newton, E. T., “‘ On the Skull, Brain, and Auditory Organ of a New Species of 
Pterosaurian (Seaphognathus Purdonz), from the Upper Lias near Whitby, York- 
shire,” Philos. Trans. Lond. 1888, vol. 179, pp. 303-687, pl. 77-78. 
