collapsible forms were used from the beginning. These forms were
constructed in six large sections, 6 ft. high, with one small key
section with wedge piece to facilitate stripping, as shown in Fig. 2.
There were three tiers of these, bolted end to end horizontally and to
each other vertically.

Above the taper base and except in the 4-ft. belt and cornice,
collapsible forms were used on the outside also. There were six sections
extending from column to column and six column sections, all bolted
together circumferentially and constructed as shown in Fig. 2. Three
tiers of these were also bolted together both vertically and
horizontally.

Having filled the top tier, the mode of operation was as follows:

All horizontal bolts in the lower inside and outside forms were removed,
as was also the small key section on the inside; this left each section
suspended to the corresponding one immediately above it by the vertical
bolts before mentioned. It is thus seen that in each case the center
tier performed the double duty of holding the upper tier, which was full
of green concrete, and the sections of the lower tier, until they were
hoisted up and again placed in position to be filled.

These lower forms were then hoisted by hand--four-part tackles being
used--and placed in position on the top forms, their bottom edges being
carefully set flush with the top edge of the form already in position,
and then bolted to it. On the outside, the column forms, and on the
inside, the wedge and key sections were set last. A 3-lb. plumb-bob on a
fine line was suspended from the inner scaffold and carefully centered
over a point set in the rock at the base. This line was in the exact