56 D. Greene—Paper Dome for an Astronomical Observatory. 
in its proper position on the model, so that its outer edges — 
formed part of the same spherical surface, and covered with — 
shellac where it was to be in contact with the paper. The 
sheet of paper cut in the proper form was then laid on the — 
model while moist, the edges turned down over the side ribs, 
and the whole placed in a hot chamber and left until thoroughly 
In this way the several sections were dried off in 
sion over the same model. The paper used is of a very supe- 
rior quality, manufactured expressly for the purpose by Messrs. _ 
Crane Brothers, of Westfield, Mass. Its thickness after dry- _ 
ing is about one-sixth of an inch, and it has a structure as com- 
succes: 
pact as that of the hardest wood, which it greatly excels in | 
strength, toughness and freedom from any liability to fracture. 
After being thoroughly painted, the several sections were 
ready to be set up side by side on the sill and connected | 
together by boiting through the adjacent ribs. The space | 
between the arch girders being left uncovered on one side from 7 
the sill to a distance of two feet beyond the zenith, the upper | 
