APRIL 11, 1884. ] 
tribution of trees in that region were a fruitful 
and congenial soil and a favorable climate. If 
the fires had never been introduced, the two 
first-named obstacles to forest-distribution in 
the prairie region would probably have been 
practically overcome by the time when the 
country was first settled; but, upon their in- 
troduction, an equilibrium of the retarding and 
accelerating forces was established and long 
continued. With the final cessation of the 
fires, and with the favoring conditions incident 
to agricultural occupancy, that equilibrium was 
destroyed, and the vigorous natural tendency 
to forest-distribution again asserted itself. It 
is now in full force except where it is checked 
by human agency ; and it is greatly accelerat- 
ed where such agency is exerted in its favor. 
It therefore only remains for the inhabitants of 
the great prairie region to decide whether their 
land shall be forested or treeless. 
C. A. Waite. 
THE APPLICATION OF PHOTOGRAPHY 
TO THE PRODUCTION OF NATURAL 
HISTORY FIGURES. 
From the accuracy and rapidity of its de- 
lineations, photography has proved itself an 
invaluable aid to science, although in natural 
history its use has been somewhat limited from 
the difficulty or impossibility of putting many 
of the objects in a vertical position. To make 
photography applicable to all classes of objects, 
it is simply necessary to have the camera so 
arranged that it may be placed at any angle 
from horizontal to vertical. The object to be 
photographed may then occupy its natural 
position, whatever that may be. For the last 
ten years, there has been in constant use, in 
the anatomical department of Cornell univer- 
sity, an apparatus constructed on this principle. 
It consists essentially of a camera fastened to 
a board that may be swung from horizontal 
to vertical, and clamped firmly at any angle. 
With this instrument have been photo- 
graphed, not only objects ordinarily photo- 
graphed with a vertical or horizontal camera, 
but delicate embryo brains and other objects 
that would collapse if removed from liquid. 
Living salamanders (Necturi) have been pho- 
tographed under water, their gills remaining 
completely outspread. 
1 Papers on this subject were given by the writer at the meet- 
ing of the American association for the advancement of science 
in 1879, and at the meeting of the Society of naturalists of the 
eastern United States in 1883. The only other persons employing 
a vertical camera in photography, known to the writer, are Dr. 
Theo. Deecke of the State lunatic-asylum at Utica, N.Y., and 
Dr. Dannadieu of Lyons, France. (For the last, see An- 
thony’s Photographic bulletin, December, 1883, p. 404.) 
SCIENCE. 
4453 
A photograph answers the requirements of 
a scientific figure in but few cases; as the 
object usually is to bring out with diagrammatic 
clearness a few details, subordinating or omit- 
ting others: hence the photograph is used as 
the basis of the figure; that is, the object is 
delineated of the desired size, all the parts 
being in their proper relative position. From 
this photographic picture may be traced all the 
outlines directly upon the drawing-paper ; thus 
avoiding the tedious labor of measurement by 
Fig. 1. — Side view of averticalcamera. A, the table supporting 
the camera; B, levelling-screws; (, shelf for holding a box 
of sand as counterpoise; D, stage upon which the object is 
placed (it is made parallel with the top of the table) ; #, camera 
with cone; F’, slotted brass guide (see fig. 2); G@, the pho- 
tographic objective (its cap is made of card-board, and covered 
with black velveteen; it is held in position by two rubber 
bands) ; H, frame hinged to the table, and supporting the came- 
ra; J, movable board to which the camera is clamped; J, head 
of the focusing-screw; K, block fastened to the movable board 
J, and containing the nut which receives the focusing-screw; 
L, semicircle by which the frame bearing the camera is set at 
any angle; J/, thumb-screw pressing against the semicircle Z, 
and serving to fix it at any point. 
the artist, and leaving all of his time available 
for artistic work proper. 
While, however, the use of the photograph 
for outlines diminishes the labor of the_ artist 
about one-half, it increases that of the prepa- 
rator; and herein lies one of its chief merits. 
The photographs being exact images of the 
preparations, the tendency will be to make 
them with greater care and delicacy, and the 
result will be less imagination and more reality 
in published scientific figures ; and the objects 
prepared with such care will be preserved for 
future reference. 
In the use of photography for figures, several 
considerations arise: 1°. The avoidance of dis- 
tortion; 2°. The adjustment of the camera to 
