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Association of American Geologists and Naturalists. 137 
He called the attention of the meeting to a style dé pomaee in dis- 
temper water colors, somewhat similar to scene painting, as ' 
adapted for geological subjects. The charts, sections, and representa- 
tions of fossils before the Association, were executed in this style ; 
also the beautiful landscapes of Mr. Russel Smith, so that: its capabilities 
could be judged of. _ This kind of painting was recommended on the 
score of cheapness, distinetness, the rapidity with which subjects may 
be executed, the ease with which corrections may be made, because it 
admits of execution on a large scale ; because it looks equally well by 
candlelight and daylight, without even requiring any particular disposi- 
tion or arrangement of lights ; and, finally, because the paintings can 
be easily” transported. ; 
The materials employed were unbleached cotton, whiting, the com- 
monest colors, and a little glue to fix them. The canvass was primed 
by whitewashing it with a mixture of water and whiting, to which about 
sy of dissolved glue was added. When the canvass was dry, a mere 
outline of the subject was sketched with a pencil, and the general tint 
and whole effect of light and shade brought out before any details were 
introduced. When the dead coloring was well executed, the finishing 
was easy. When the ground tint was dry, the details could be marked 
with pencil and put in with shadow tint. ‘Then a few judicious touches 
with shade tint finished the design. If a clear and distinct effect was re- 
quired, the color should be laid on a dry ground ; if it was desired that — 
the tints should blend together, they should be laid on damp ground. ; 
Any degree of contrast of light and shade could” be effected in this’ 
style. 
As a proof of the rapidity with which subjects might be ‘ibe in 
this way Dr. O. stated to the meeting, that he had in four months 
— nearly eight hundred meee of organic remains, inclusive of 
painting or water colors on agree 
After the reading of tl ‘Deen } paper, the subject of minera- 
logical classification was again introduced. Mr. J. D. Dana at % 
the request of the Chair, stated that he had preferred the natural 
history arrangement, as being best calculated for instruction, and 
giving the most satisfactory view of the relationship of the several 
species and families. The arrangement adopted by him in his 
work on mineralogy, was based on the classification of Mohs, 
‘and was in truth mainly a chemical system, in which either the 
acid or the base was selected as the characterizing feature, accor- 
Vol. xv, No. 1.—April-June, 1843. 18 
sh 
