When whalemen refused to use poison
harpoons, they sought another way to fasten to and kill the whale
simultaneously. This remained a desired improvement, especially
whaling in the ice fields of the northern fisheries. In place
of poison, development of the harpoon turned to explosives.
The first explosive hand-darted harpoon
patented in the United States was invented by Albert Moore of
Hampden, Maine in 1844 (U.S. Patent No. 3,490, 
March 16, 1844). His harpoon, fashioned after
the single-flued harpoon, had a single barb that pivoted on an
iron pin. When the barb was closed, in the darting position,
a small wood pin was inserted through holes drilled through the
head and shank. A cavity in the single barb opened to the rear,
and accepted a small glass vial of explosive which was held in
place by a wood peg across the opening. Moore described the action
of his harpoon in the patent specifications:
As soon as the harpoon is thrown into the whale and fastened to it the wooden pin is broken by the power of the whale pulling upon the tow-line attached to the harpoon, and the fluke of said harpoon will open or turn upon the iron rivet, and in opening or turning upon said rivet will come in contact with the vial and break it, will produce friction, and cause the powder to explode, which will destroy the whale.
Albert Moore patent drawings.
Moore described the preparation of
the explosive, but indicated that any suitable explosive could
be used. There was no other fuse or other positive means to ignite
the explosive. If the explosion were great enough to kill the
whale, it certainly would have destroyed the harpoon. No examples
of the Albert Moore harpoon have been found.
Another explosive harpoon was patented
in 1851 by Charles Burt of Belfast, Maine (U.S. Patent No. 8,073,
May 6, 1851). The explosive force was not intended to be so great
as to kill the whale by its force, but rather to fire a projectile,
the harpoon tip, into the whale like a bullet. The 
general appearance was similar to the single
flue-irons. Nested under the flue was a 
trigger that depressed when the resistance
of the blubber pressed on it when withdrawal forces were applied.
The trigger actuated a firing mechanism in the head. A one-half
inch diameter stud at the rear of the separable tip was inserted
into a bore through the head acting as a gun barrel. A patch
of linen made the stud a tight fit in the barrel to hold it in
place until it was propelled by the explosive. During darting
the single flue protected the trigger. A pull on the whale line
caused the trigger to be depressed releasing the firing mechanism.
According to the patent specifications, this caused the separable
tip "...to be forced off by the explosion, in order to kill
the whale immediately."
Charles
Burt Explosive Harpoon Patent Drawings
Theodore Briggs of Philadelphia,
Pennsylvania patented an explosive hand-darted harpoon in 1860
(U.S. Patent No. 30,869, Dec. 11, 1860). This iron was made with
pivot barbs on the shank behind the explosive head. These barbs
were to open outward to secure the whale after the head exploded
to kill it. The head of the harpoon consisted of two metal tubes
connected end to end by means of a threaded plug. The plug was
made with a nipple for a percussion cap extending into the rear
tube of the head; it also had a small hole through its length
to transmit fire from the percussion cap to the forward tube.
The forward tube was made with a solid, pointed tip for penetrating
the whale during darting, and was filled with gunpowder. The
assembled explosive head was not forged to the shank, but fit
loosely over the end of it. The solid shank entered the hollow
rear tube a short distance. A small wood 
shear pin held the head to the shank for
darting; the end of the shank was thereby held a short distance
back from the threaded plug with the percussion cap on it.
Pivot barbs were installed in a mortise through a widened section of the shank, and they pivoted on a single, common pin. The two pivot barbs were spring-loaded open by small leaf springs mounted to the shank. A sliding collarover the ends of the barbs held them in the darting position. The aft end of the shank terminated in a forged socket for mounting the iron to a wood pole, the same as standard hand-darted harpoons. In his patent specifications Briggs described the action of his harpoon:
Patent drawings for the Theodore Briggs explosive harpoon.
It is thrown by hand in the usual manner, so as to cause it to penetrate the skin and thick mass of blubber of the whale, and the tubular end then coming in contact with bone is suddenly arrested, while the momentum of the body and balance-shaft of the implement causes the breaking of the wooden pin ... and the consequent driving up of the stem end ... against the percussion-cap on the nipple ... exploding it and the powder ... thus destroying the life of the animal almost instantly.
During penetration the resistance of the blubber caused the sliding collar to move back to release the spring-loaded pivot barbs that would then open to secure the whale.
If the wood shear pin was weak, the
initial impact against the side of the whale could have caused
an explosion before penetration. If the shear pin was strong
enough to to resist breaking during penetration, and the harpoon
did not hit bone the mechanism would not function. It would be
very unlikely that the harpooner could dart the iron to hit bone.
The Briggs harpoon was never popular. No example of this explosive
harpoon could be found.
In 1865 Silas Barker of Hartford,
Connecticut patented another explosive hand-darted harpoon (U.S.
Patent No. 46,437, Feb. 21, 1865). This harpoon shot an explosive
head farther into the 
whale before exploding. The hollow head was
filled with gunpowder and sharp, angular pieces of steel to act
as shrapnel. A long hollow tube filled with explosive was screwed
into the rear of the head. This tube acted as a time fuse, igniting
the powder in the head through a small hole at the forward end
of the tube after the propelling charge had ignited that far.
The tube fit into a corresponding hole that acted as a gun barrel
in the stationary portion of the head which contained a firing
mechanism.
The patent specifications describe a trigger
wire extending from the hammer of the firing mechanism back along
the shaft of the harpoon to a crosspiece. When the iron was darted,
the resistance of the blubber on the crosspiece caused the wire
to be drawn back, releasing the firing mechanism and igniting
the explosive to propel the head farther into the whale. The
crosspiece was described as a ring of thin metal positioned edgewise
around the shank. The ring also attached to a "discharging-rod"
that acted as a trigger, parallel to the shank. In the event
that penetration was insufficient to allow the blubber to act
on the crosspiece, a small line was provided by which the harpooner
could actuate the mechanism manually. A large brass toggle barb
acted to secure the whale after darting. The choice of brass
may have been to prevent any spark that may have ignited the
powder prematurely; otherwise brass was weaker than iron, and
would have caused corrosion when in contact with iron. This toggle
barb was farther back on the head so it would not have been damaged
by the explosive. More of this detail can be seen on the patent
model, and patent drawings, which differ somewhat from the actual
iron that was produced. The Silas Barker explosive harpoon is
vey rare; not many were made or used.
Silas
Barker Patent Drawings (above) and patent Model (left).
Zeno Kelley had a watch repair business
in New Bedford, and repaired and adjusted 
chronometers for the whaleships. Whaling
captains congregated in his shop to talk about whaling, and Zeno
was very much involved in their business. In 1868 he was granted
a patent for a hand-darted explosive harpoon (U.S. Patent No.78,673,
June 9, 1868). The head of his harpoon was made hollow and filled
with gunpowder. The iron was mounted on a standard iron pole
and was hand darted. The mechanism that detonated the powder
was the feature claimed in the patent. A percussion cap was placed
on a nipple at the rear of the explosive head. The hammer to
strike the cap was a metal rod forced against the cap by a coil
spring. This mechanism was enclosed in a widened section of the
harpoon shaft at the head. A pin placed through the rear of the
hammer rod connected it to a sliding cover plate on the outside
of the wide part of the shaft, over the firing mechanism. The
plate was drawn back to cock the hammer. A pivot barb set in
a mortise of the wide section acted to engage the hammer and
hold it in the cocked position. When the pivot barb was in a
streamlined darting position, and the sliding cover was drawn
back, a small hole in the cover plate was aligned with a corresponding
hole in the barb. A small metal pin inserted through these holes
held the hammer in the cocked position. After the iron was darted
and a force applied to the whale line, the rear tip of the barb
caught in the flesh and caused the barb to open; this also pulled
the metal pin through the hole in the cover plate and released
the hammer to strike the percussion cap, and explode the head
in the whale.
Zeno Kelley Explosive Harpoon Patent Drawings
In the patent Kelley stated that
the harpoon could also be used as a gun harpoon, shooting it
into a whale from a shoulder gun. For that, Kelley suggested
mounting the iron on a short rod to fit a gun barrel, rather
than an iron pole. To fasten the whaleline Kelley provided a
cast iron slide that fit loosely around the harpoon shaft, forward
of the socket. To minimize the recoil forces that could snap
the whale line due to the sudden tension imparted to it when
the iron first left the gun barrel, a coil spring was positioned
around the shaft between the socket and the slide. This spring
was to act as a shock absorber to lessen the sudden impact on
the whale line. Kelley used this feature on an earlier gun harpoon
patent, in 1867, for a non-explosive gun harpoon. This sliding
collar and coil spring feature seems to be included here as a
second thought.
Charles Freeman Explosive Harpoon (above) and Detail (below). Length is 41". Head is 4-3/4" long, 4" wide and 11/16" thick.
In 1872 Charles Freeman of Brewster, Massachusettes patented an explosive-head harpoon (U.S. Patent No. 126,388, May 7, 1872). In The Whale Fishery and Its Appliances, 1883, James Templeman Brown said this iron, charged with 3/4 lb. of gunpowder, was used for killing finback whales off the coast of Cape Cod in Massachusettes.
The cast iron head of the Freeman
iron was hollow and filled with gunpowder. A time fuse with a
short stem was attached to the
rear of the head. A percussion cap was placed on a nipple at
the rear of the stem which fit into a corresponding hole in the
forward part of a widened shank section. This section was made
to form a flat base on which the head was mounted. A screw through
the toe of the base secured the explosive head to the harpoon.
The widened shank also contained the firing mechanism. The hammer
of the firing mechanism was a metal rod, forced against the percussion
cap at the base of the head by a coil spring. A small spring-loaded
latch held the hammer in the cocked position. A large iron pivot
barb at the side of the shank, opposite the screw securing the
head, acted as a trigger. During penetration the resistance of
the blubber pushed the pivot barb in toward the shank. This action
resulted in the barb pressing against the latch holding the hammer,
causing it to release the firing mechanism and exploding the
head.
Charles Freeman Harpoon Patent Drawings
On some examples of the Freeman iron a small safety lever was provided to prevent actuating the barb inadvertantly. Most Freeman irons were made with two small stationary barbs brazed or forge welded to the shank to make withdrawal more difficult, preventing the iron from working its way out. However, there are some examples of the Freeman iron which do not have these small shank barbs.
There were several Freeman irons made, but they were never very popular, probably because the explosion would have destroyed the harpoon and its barb, and possibly would have blown the iron back out of the whale.
Bibliography Harpoons History Knives Lances Links Markings Non-Whaling
Patents Poison Processing Shoulder-Guns Shoulder-gun Irons Spades Swivel Guns and Irons