88 PROCEEDINGS: BOSTON SOCIETY NATURAL HISTORY. 
partial submergence of the second; and the fifth exhibited the old 
denuded plateau, or peneplain, revived into new youth by elevation. 
A few sets of these models were made by Mr. Emerton and 
sold to schools and colleges, but they are now “out-of print.” 
The set in my own laboratory has been in active use for ten years 
past. Selections from it have travelled as far as Philadelphia, 
Baltimore, and Washington to illustrate lectures; some have been 
sent to Boston,'Brooklyn, and Chicago for exhibition; a number of 
them have accompanied me to teachers’ meetings in different parts 
of New England. It is natural, therefore, that they show signs of 
wear. They have been used with especial acceptance in my summer 
course in physiography for two years past; many teachers inquiring 
whether copies of them could be had, and declaring their emphatic 
belief that with such aids it would be easy to teach many facts and 
principles that now seem too difficult for the pupils of secondary 
schools. That such is the case has been my feeling for some years, 
and hence I have greatly desired to revise the models in various 
respects. A new edition should be constructed with greater care, 
and adapted particularly to such a course in physiography as may, 
I trust before long, be accepted among the alternative subjects for 
admission to college. 
It has been by good fortune possible to undertake this revision 
during the past year. A considerable fund for the expenses of the 
work was contributed by a number of ladies and gentlemen of 
Boston, whose names would be familiar from their frequent associ¬ 
ation with educational or philanthropic undertakings. Of these, I 
must mention in particular Miss Marian C. Jackson, without whose 
kind interest in my plans, the measure of success thus far attained 
would have been impossible. During the winter of 1895-96, Mr. 
G. C. Curtis, then a fourth-year student in the Lawrence Scientific 
School, devoted part of his time to designing and constructing a 
model of composite topography, and thus gained good prepara¬ 
tion for the desired work. Through the past winter, he has been 
engaged, under my constant supervision, in constructing the first 
numbers of a series of models in wax, and copying them in plaster. 
Some account of his method is appended to this paper. We have 
finally had the expert assistance of Mr. John L. Gardner, 2d, in 
photographing the uncolored plaster casts, as here reproduced in 
four plates, the fourth containing two oblique views of the third 
model. In their final form, they will be simply colored to bring out 
their natural divisions more distinctly than is possible in a monotint. 
