36 BULLETIN 1191, U. S. DEPARTMENT OF AGRICULTURE. 
MOWING. 
The fourth method of harvesting, used by all the large establish- 
ments, consists in mowing the kelp. For this purpose a vessel is 
equipped with a more or less complex machine, of which the essen- 
tial parts are a horizontal cutting blade working on the same prin- 
ciple as a mower knife, at a depth of about 4 feet, and an endless 
chain elevator, or “ draper,” which hoists the kelp on board. Vari- 
ous types of vessel have been used, but in all that have been operated 
successfully the harvesting mechanism is placed in the bow, the 
blade cutting directly ahead of the boat. The length of the knife 
is considerably less than the beam of the boat, the largest harvesters 
cutting a swath some 20 feet wide and the smallest about 10. The 
elevator has the same width as the swath. Its lower sprocket wheels 
are immediately back of the cutter bar, and it is driven at rather 
high speed, so as to pick up the cut kelp before the waves wash it 
away. A knife at each side of the elevator, and parallel with it, 
serves as an edging knife to cut the kelp clear at the sides. There 
being no tough, hard fiber in kelp, the knives cut properly at about 
one-fourth the speed at which a mower knife must work. A gasoline 
motor drives the harvesting mechanism. When not in actual opera- 
tion the knives are hoisted out of the water. The great bulk and 
weight of machinery in the bow of a kelp harvester make it difficult 
to steer, especially in rough weather. Such a device as described 
above, when properly adjusted, may cut a hundred tons of kelp with- 
out uprooting a plant. However, if the weather is rough, or if the 
knives are not kept running properly, it may uproot large numbers of 
plants. The elevator fails to pick up many of the fronds and they 
are washed away by the waves. Sometimes nearly half the kelp 
cut is thus set adrift. Various methods are used in loading the kelp 
after it is brought aboard. ‘ 
METHODS. 
Two methods of mowing have been employed: cutting systemati- 
cally up and down or round and round a bed, as in cutting hay; and 
running the harvester through the bed so as to cut the thicker por- 
tions only. The first method was employed by the Hercules Powder 
Co., with good results. By employing three large capacity harvesters 
sunultaneously, which cut one behind the other, only a small propor- 
tion of the kelp was lost, as one harvester picked up what the one be- 
fore it sct adrift. Rapid and thorough cutting tended to keep black 
rot under control and to protect the new growth that came up almost 
immediately after cutting from molestation. The disadvantage 
connected with this method is the loss of time and labor in cutting 
over thin portions of the bed. 
COMPARISON OF METHODS. 
The second method of cutting is the one that has usually been 
employed. It has the outstanding advantage of saving time at 
the start and of insuring the getting of the best kelp. When 
several companies are cutting in the same bed, there is often con- 
siderable competition for the best portions. An advantageous modi- 
fication of this method is to avoid cutting to the edge of the bed, 
