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Located
near the Northern end of Lake Huron, Spectacle Reef has
approximately 170 miles of open water to the Southeast. The
lighthouse was to be positioned on the Northern end of the reef
to help protect it from the havoc of Lake Huron. Strong
Northwestward gales often create monstrous waves that pound the
reef and in the winter and spring months these winds can push
large sheets of ice. Often 2 to 3 feet thick and covering
thousands of acres of water, these large masses are almost
unstoppable once in motion with destructive forces. A
combination of construction techniques, both crib and cofferdam,
would be used to help withstand mother nature.
A crib built of 12 inch timbers sheathed with
steel plates, measuring 92 feet square by 24 feet high with a 42
foot open center, was constructed at the base camp. At this
time, wreckage and iron ore from the 1867 foundering of
NIGHTINGALE was removed from the reef. On July 18, 1871, the
crib was towed out to the reef by the tugs CHAMPION and
MAGNET along with a number of other vessels. Once in
position the following morning, the crib was filled with rock
and grounded in position. This crib extended 12 feet above the
water providing protection from waves and ice for the crews
quarters, cofferdam and landing craft. The crib would eventually
be filled with cement forming what is now seen as the square
base around the lighthouse. Once the temporary crews quarters
were constructed, a Fourth Order Fresnel lens was installed on
the roof of one to help guide mariners during it's construction.
A
cofferdam of 41 feet in diameter was then constructed inside the
crib. It's construction was of 4 x 6 timbers held in place by
timber braces and steel straps around it's exterior. The
cofferdam was then sealed with portage concrete and pumped free
of water. This allowed workers to manually flatten the now dry
area of the reef in preparation for the limestone foundation
blocks.
In a quarry in Marblehead, Ohio, blocks of
limestone measuring 2 feet thick were precisely cut to interlock
with each other and delivered to Spectacle Reef. Each course of
block was then set and fastened together with 2 1/2 inch
diameter x 2 feet long wrought iron bolts. Bolts measuring 3
feet in length enter the reef bedrock 21 inches, lock the first
course in place. The following courses, once in position, were
then diamond drilled and locked with bolts entering each
preceding course by 9 inches. The bolts are wedge shaped at both
ends and locked in place with portland cement. Fitting of the
first course took approximately two weeks to complete and each
of the following courses took only 3 days to fit, drill and
bolt.
The stone conical tower measures 32 feet in
diameter at the base extending up 93 feet. The tower is solid
for the first 34 feet with the remaining 59 feet containing 5
rooms measuring 14 feet in diameter with various ceilings. The
tower walls measure 5 feet 6 inches at the base and taper to 16
inches at the top. Construction of the lighthouse was nearly
complete with its tower now standing. The winter of 1873 was now
setting in and final construction had to be held off until spring.
The winter of 1873-1874 put the lighthouse
construction to a test and delayed it's completion. Ice had
piled on the reef to a height of 30 feet around the lighthouse
and had to be cut away to gain entrance to the doorway. A large
Second Order Fresnel lens was then installed within the cast
iron lantern room producing a lens focal plane at 86 feet above
the water level and 97 feet above the reef bedrock.
For
navigational aid in the fog, the station is equipped with an
air-diaphone fog signal. As seen in the early Coast Guard photo
above, there were also 2 attached out-buildings, today only one
remains. |