26 
maps, or, at all events, the main features, he believed, were 
laid down on a scale suiRciently large to admit of the prin- 
cipal mineral features being suiRciently delineated. Mr. S. 
exhibited a number of small hand models, by which the na- 
ture of plans and sections were illustrated, and from which 
it appears how difficult it is to obtain a correct projection of 
the contour of objects, varpng so much in curvature and 
inclination as the outcrops of strata usually do. He explained 
the mode of constructing such, hand models, which, he be- 
lieved, might prove of considerable use in extending a gene- 
ral knowledge of geological features ; for there were many 
phenomena which could not be clearly comprehended by the 
mere use of planes only. He would instance the V form 
which strata present in valleys ; the point of the V being in 
some places up the valley, and at other places down the 
valley. Now this was believed by many persons to indicate 
a different inclination of the strata ; but by the two models 
which he exhibited, it was apparent that in both cases the 
inclination was the same, and that the V assumed these po- 
sitions accordingly as the strata were more or less steep than 
the descent of the valley. The great perplexity frequently 
caused by slip dykes, and by axes of elevation, could thus 
be presented at once to the eye ; and the simplicity of con- 
structing such models, combined with their extensive utility, 
would doubtless lead to their being more generally used. 
The Isometrical Drawing which he had presented to the So- 
ciety was a medium between the common ground plan and 
the model. — Mr. S. then stated, that to the late Professor 
Farish, of Cambridge, the merit of originating this beautiful 
method of projection was due. That gentleman had frequent 
occasion to construct rude drawings, to enable his workmen 
to put models of machinery together ; and it was this that 
suggested to him the adoption of a method of drawing which, 
instead of only she\sdng one side of a cube, should present 
three sides at once to view ; and this Mr. S. showed, by a 
