ADAM SEDGWICK AXD WILLIAM BUCKLAND. 
139 
some portions of the formation, and his classification of the series is 
the one that is still held, with slight modification. His description 
of the Magnesian Limestone must be regarded as the most complete 
production of Professor Sedgwick's pen, and there was probably 
nothing published at that period of geological history which can be 
compared to Sedgwick's Monographs for thorough completeness and 
mastery of his subject. The great unconformity between the Coal 
Measures and the Magnesian Limestone is pointed out by Professor 
Sedgwick. He says : — " After the production of the rocks of the 
carboniferous order, the earth's surface appears to have been acted 
upon by powerfully disturbing forces, which, not only in the British 
Islands but throughout the greater part of the European basis, pro- 
duced a series of formations of very great extent and complexity of 
structure. These deposits, known in our country by the name of 
New Red Sandstone and Red Marl, and when considered on an exten- 
sive scale comprising all the formations between the Coal Measures 
and the Lias, notwithstanding their violent mechanical origin have 
several characters in common which enables us to connect them 
together, and for general purposes of comparison to register them as 
one group ;" and he continues : — " We have no right to assume, nor 
is there any reason to believe that such disturbing forces either acted 
uniformly or simultaneously throughout the world. Formations 
which in one country are unconformable may in another be 
parallel to each other, and so intimately connected as to appear 
the production of one epoch." It was probably the observation of 
the remarkable formations presented by the concretionaiy character 
of the Magnesian Limestone that induced Sedgwick to turn his 
attention to the causes of these peculiarities, and led to the production 
of his paper on the " Structure of large Mineral Masses, and especially 
on the chemical changes produced in the aggTegation of stratified 
rocks during different periods after their deposition," which was read 
at the Geological Society in 1835. It contains an excellent discussion 
on the phenomena of metamorphism, concretionary structure, cleavage, 
and joints. The terms "cleavage" and "strike" were first intro- 
duced into geological literature in this paper. Meanwhile he Iiad 
been engaged, sometimes alone, sometimes in company with Sir 
