APPENDIX D. 
REMARKS UPON THE CONSTRUCTION OF THE MAPS. 
The plan of construction of these maps is, in some respects, new. It however embraces a 
system of topography at one time adopted in France, in which the light is supposed to fall at 
an oblique angle upon the objects represented; illuminating certain portions, and leaving others 
in shade ; 
A disadvantage of that system, in copper and steel engraving, was, that it afforded no relief 
to the light sides of the mountains or ravines, which, in many cases, therefore could not be dis- 
tinguished from the surrounding plain. 
In lithographed maps, printed in black and white, upon tinted paper, this objection could, 
in a measure, be obviated. 
Mr. Egloffstein, the topographer to the expedition, conceived the idea—while sketching the 
naked mountains, barren plains, and immense gorges that characterized some portion of the 
region explored—of endeavoring to give to his map the appearance of a small plaster model 
of the country, with the light falling upon it at a particular angle. Such a model of a bare 
and rocky region would strongly resemble nature. Portions of the mountain sides and of the 
edges of the ravines would appear in brilliant light, others in deep shade. Level plateaus 
and valleys would have a uniform tint; the lightness or darkness of which would depend upon 
their elevation or depression. Mr. Egloffstein devised the plan of producing the different tints 
___ by means of fine parallel lines, drawn upon the plate with a ruling machine; each part of the 
.... ruled portion being brought to the requisite shade by exposing it a longer or shorter time to 
- “4 action of acid. The maps were engraved by him in accordance with this plan. The topo- 
aphy was constructed from the field-notes directly upon the plates. The latter were of steel; 
it being feared that copper would not be hard enough to give a sufficient number of impressions 
of the more delicate tints. The topography was first delineated; the lettering was then put 
on; and afterwards the plates were ruled. 
A glance at the result will show how far the experiment has succeeded. There are defects 
readily to be perceived, and further experience will doubtless suggest many improvements, but 
I think it will be generally admitted that, for maps of such a character of country, and upon 
such a scale, this style—which is believed to be new, so far a regards the application of the 
_ ruled tints—is, in beauty and effectiveness, much superior to the old. It possesses the power, 
_ which the other does not, of exhibiting the comparative altitudes of plateaus of different ele- 
_ vations. This is particularly apparent in map No. 2. The alluvial lands along the Colorado 
and Flax rivers, being designated by a darker tint, are distinctly defined, as well as the bound- 
aries and extent of the mesas that limit them. The loftier table-lands, by their lighter ap- 
‘ pe rance, may also be distinguished from lower levels. In the old style these effects could not 
_ be produced. 
_ This method of representing topography is less conventional than the other, and truer to 
nature. It is an approximation to a bird’s eye view, and is intelligible to every eye. 
_ Another advantage of the system is its economy. Nearly one-half of the most expensive 
‘t of map engraving—the hachures upon the mountain sides—is dispensed with, and the ad- 
nal work, the ruling, is attended with little cost. 
