110 PROCEEDINGS : BOSTON SOCIETY NATURAL HISTORY. 
and a corresponding development of terraces in the valley doors 
among the mountains was given. The volcano and its lava dows 
were built up in an essentially accidental relation to the pre-exist¬ 
ent topography. The negative from this enlarged model was then 
cut off at the landward end, so as to reduce its length to the same 
measure as that of the others. 
In all the models, the production of a perfect sea surface has been 
a matter of no little difficulty. In the drst model, the sea was drst 
scraped as smooth as possible with a steel straight-edge, and then 
planed true on the plaster negative. ' The sea of the horded coast 
was made by planing the plaster negative, as stated above; the 
chief difficulty here was to reduce the different parts of the negative 
uniformly, and to stop with a true plane surface when the desired 
irregularity of shore dine was reached. In the sea bordering the 
coastal plain, the wax was scraped down and the negative planed 
off, as in the first model. 
The construction of these models is a form of creative work, the 
labor of modeling being similar to that of the sculptor’s work in clay. 
The modeler must understand, not only the geographic history of 
the region which he depicts, but must grasp the essentials of 
form which characterize such, a territory and topography. The 
work differs essentially from the modeling of mapped localities, 
which is a mechanical process of reduplication in three dimensions. 
The differences of the two arts might be compared with those of 
the photographer and the landscape artist. 
Printed, July, IS97. 
