27 
diagram, was at once effected by inscribing a hexagon in a 
circle, and uniting the angles. By means of a protractor, 
constructed for the purpose, any angle might be at once 
projected on any one of the three sides of the cube thus pre_ 
sented to view ; and, keeping in mind the cube, as the type 
and origin of this method of projection, it would easily be 
understood, that every plane surface parallel to any one of 
these three sides could be at once correctly delineated, by 
principles exactly similar to those on which the common 
ground plan and section are constructed. — Mr. Sopwith ex- 
hibited a diagram of faint blue lines, by which the process 
of Isometrical Projection is greatly facilitated ; and also an 
instrument which he had contrived, by means of which the 
principal points of a common plan could be transferred to the 
respective positions required in isometrical drawing. Mr. S. 
then described the principal geological features of the Iso- 
metrical drawing, which was exhibited, and which repre- 
sents an interesting portion of the mining district of Alston 
Moor. Several vertical sections are combined with a pic- 
torial representation of the surface, on which the roads, 
fields, houses, trees, &c., are delineated. 
Mr. Sopwith also exhibited a section of the Carboniferous 
or Mountain Limestone formation, from Hownes Gill to the 
summit of CrossfiU Mountain, a distance of 28 miles. This 
section formed part of a larger one, across the island, from 
Whitehaven to Monkwearmouth, near Sunderland, which 
had been divided into four parts. The first comprised the 
Whitehaven Coal Field, and was to be executed by Mr. 
Williamson Peile. The second contained the Cambrian 
Rocks, and was undertaken by Professor Sedgwick. The 
third was the one now shown, representing the Carbonifer- 
ous Limestone ; and the fourth exhibited the Newcastle 
Coal Field, and would be executed by Mr. Buddie. 
