showing the
main workbench and the collection of clockmakers' tools. (_Courtesy of
Museo Nazionale della Scienza e della Tecnica, Milan._)]

[Illustration: Figure 24.--FUSEE CUTTER used by Bertolla. Now in the
collection of the Museo Nazionale della Scienza e della Tecnica,
Milan.]

[Illustration: Figure 25.--INTERIOR OF BERTOLLA'S WORKSHOP, showing
details of paneling and floor case with Bertolla manuscripts. (_Courtesy
of Museo Nazionale della Scienza e della Tecnica, Milan._)]

According to Pippa,[19] certain characteristics become apparent in a
study of the surviving clocks by Bertolla. The tall-case clocks are
narrow and range in height from 7-3/4 feet to 10-1/2 feet. The cases had
this excessive height in order to obtain the greatest fall for the month
and year movements which Bertolla constructed. For the weight assembly,
he substituted a drum wound with a key at the point of the driving wheel
in place of the customary pulley. The addition of an intermediate wheel
augmented the drop of the weight.

Bertolla's movements were solidly constructed from well-hammered brass
and iron. He favored the recoil anchor escapement in his clocks and the
Graham dead-beat anchor escapement with a seconds' pendulum. The
escapement was not always placed in the traditional location in the
upper center between the plates. Bertolla occasionally displaced the
pendulum to one side, to the lower part of the movement or placed it
entirely between two other small plates.[20]

He utilized every type of striking work, including the music-box
cylinder common in the clocks of the Black Forest and the rack and
snail. Bertolla most frequently employed the hour strike and _grand
sonnerie_. He often used a single hammer on two bells of different sound
with the rack and snail. An example of this type is the clock he
produced at the age of 80. To achieve the necessary axis of rotation for
the hammer, which is perpendicular to the plate when it strikes the
hours, it moves to an oblique position and displaces one of the two long
pins in an elongated opening.

Bertolla's dial plates were generally well executed, with a raised or
separate chapter ring applied to a brass or copper plate, such as a
copper-plate _repousse_ and gilt with baroque motifs, or upon a smooth
brass plate with spandrels of _repousse_ work usually of silver, in
relief and attached. The engraving of the chapter rings was excellent.
The hands were well executed in steel or per