CURTIS : THE HARVARD GEOGRAPHICAL MODELS. 109 
so that their design might be essentially true to nature ; but further 
than this, no forms were introduced for which a reasonable physio¬ 
graphic explanation could not be given. Only in this way can arbi¬ 
trary and impossible combinations of form be avoided. It is true, 
that, in the later construction of the models, the specifications of 
the drawings were departed from in a number of particulars; 
yet the guiding principles according to which the drawings were 
designed were followed throughout. The models are, therefore, 
of the same order of verity as a picture of a human face would be, 
if designed as a type by an artist familiar with the essential com¬ 
bination of human features. The series of drawings goes further 
than the models now constructed ; but it is hoped that the later 
forms, already prepared on the maps, may eventually be reproduced 
in relief also. 
When the drawings had reached an acceptable stage of detail, 
they were reproduced in modeling wax, a specially prepared form 
of beeswax, procured of Messrs. Wadsworth and Howland, Boston. 
This proved to be a very satisfactory material for modeling. It 
is easily worked, is susceptible of taking much detail of form, and 
retains its form unchanged for months at a time. Being free from 
moisture, it does not cause the modeling board to warp. By slight 
warming, it becomes plastic, so that it can be roughly shaped almost 
as easily as moist clay. The blocked-out ridges, made by hand, 
were then carefully carved, for the most part with steel tools, into 
more detailed expression; photographs selected from the Gardner 
collection, and plates in various geological reports being a constant 
guide in this part of the undertaking. 
After the first model was completed, several plaster negatives 
were taken from it in the ordinary manner. The horded coast of 
the third model was then produced by planing down the sea level 
in one of the negatives. Upon a positive from this modified nega¬ 
tive, the headland cliffs were cut and bayhead deltas added, a slight 
modification was made in the land slopes, and the glaciers were 
somewhat curtailed, on account of the depression of the region and 
the consequent tempering of the mountain climate. The positive, 
thus altered, served as the original for negatives and casts in turn. 
The coastal plain was built forward on the original wax model, by 
adding a new sea level in the foreground, and reducing the wax 
forming the former sea level to the inclined surface of the plain. 
The valleys of the extended streams were then carved in the plain, 
