Notice of a Geological Model. 81 
mits of shewing the objects solidly, in relief; and according to 
their actual proportions, whene ever practi icable. I mean the pro- 
cess of modelling areas of country, in preference to any other 
method of representation; whether by drafts, diagrams, tables, 
maps, sections or other customary means. Under this impression, 
and with a view to convey these sentiments in a useful direction, 
[ have made some exertion to complete, for this occasion, a spe- 
cimentit the art, illustrative of several hundred square miles of 
interesting country in the interior of this state; but have only 
during the intervals of the present meeting of geotniaiate, found 
time to re and commit to paper the following observations. 
_ With the best assistance which art can confer, by means of 
horizontal or vertical or concentric shading, or by the most elabo- 
rate arrangement of lines upon a plane surface, to produce the 
effects of light, shadow, height, depth and perspective, such pro= 
cesses, it is universally conceded, fail to accomplish what is sim- 
ply effected by es If to these desiderata in geological 
to represent the courses and the inclination of strata, and the 
breadths and separate characters of formations, the difliculties 
attendant on lucid illustration are mneneeen, in any process short 
of modelling. 
Whenever the scale, upon which a given area is protracted, is 
sufficiently large to permit an approximate correspondence be- 
tween the horizontal and the vertical admeasurements, the effect 
is perfect. ‘The utility of the work is enhanced, in as much as 
it combines the exhibition of both transverse and oe sec- 
tions on the field of survey ; and illustrates not only the e 
features and physical geography of the district, but enables the 
interior structure, the grouping of its mountain masses, a 
nations, bearing, direction, contortions and dislocations of the 
strata into which those formations and masses are subdivided, to 
be exhibited in a simple yet very striking and appropriate manner. 
With the addition of superficial coloring, the pictorial character 
of the region represented, can be as accurately depicted as ina 
highly finished landscape. Perhaps even more so; in as much 
as the positions of all surrounding objects, and of all accessory de- 
tails, are defined with geognostic accuracy in the one case, rather 
ines which are indispensable to _ 
we add those which are inten- 
* 
than imperfectly traced in the other, however experienced may — 
Vol. xu1, No. 1.—April-June, 1841. 
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