FRENCH'S IMPROVEMENT,
For Operating and Fastening
TRAP DOORS,
(PATENT APPLIED FOR)
These Doors are always
fastened; can be opened and closed by a boy.
Can never fall and break.
Can be opened any distance
for ventilation.
Cannot be opened without
the key.
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Our Ventilating Cover.
SECTION OF
VENTILATING COVER,
CUT THROUGH THE MIDDLE,
AND SHOWING IT LAID IN THE WALK.
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Affords a constant ventilation
to the Vault and is so made that water and dirt cannot
get into it, while the air has a free circulation.
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