FRESH-WATER MUSSELS AND MUSSEL INDUSTRIES. 49 
string is to be substituted. The soft line wears better than any other kind, especially 
where the bottom has much sand and gravel. Chains, or long wire links, are sometimes 
used in place of the cotton twine, but, although they last much longer, they are not 
often employed, owing to the extra weight and cost. Each line carries from two to six 
hooks, attached at intervals of sufficient distance to prevent successive hooks from 
interfering with one another. 
The bridle is a small-sized rope, about 0.5 inch in diameter, and is attached to the 
bar near the ends. It is left loose, so that it may be tied to the main rope about 2 feet 
above the middle of the bar. 
The main rope, or cable, is larger, being usually about 0.75 or 1 inch in diameter, 
while its length varies according to the depth of water, generally from 25 to 35 feet 
being required. ‘The rope is tied to the middle of the bar and to the center of the bridle. 
To obviate difficulty from twisting and to make the rope available when desired for 
other purposes, the attachment to the bridle is usually made by a swivel snap and ring. 
The mule.—An essential feature of the outfit with this method of fishery, under 
ordinary conditions, is the underwater sail or mule, as it is called. When the mussel 
fisherman is ready for work and the boat is over the shell bed, the bar is thrown over- 
board. The hooks of the bar catch in the river bottom, as well as in the shells, and thus, 
acting as anchors, will stop the progress of the boat downstream, unless additional power 
is supplied. In order to derive this power from the current, the mule is lowered into 
the river at the stern of the boat, to which it is connected by guide lines. Its broad 
surface is at right angles to the current, and the entire outfit is thus forced slowly down 
the river, stern first, in spite of the drag on the bottom. By means of the guide lines 
the mule is easily regulated to steer the boat at a desired angle over the mussel bed, or 
to avoid a familiar snag. 
There are two well-known types of mules in use on the different rivers—the common 
frame type and the roll mule. 
The frame type is rectangular in form, the outline or framework consisting of light 
strips or narrow boards about 3 inches wide by 0.75 of an inch thick, sometimes with a 
center strip extending from the middle of the bottom to a few inches above the top. In 
Plate X XVII, figure 1, a mule is shown lying on the stern of the boat; see also Plate 
XXIX, figure 1. The frame is covered with strong cloth, such as muslin, canvas, tar- 
paulin, gunny sacking, etc., which is left rather baggy in order to make the appliance 
more steady in the water; otherwise when the current strikes it at an angle it is liable 
to turn over, dart forward, and ‘‘kick.’’ This characteristic accounts for its technical 
designation as ‘‘mule.” It is connected to the boat by lines running from the four 
corners, excepting for those patterns having the center strip, when three connections 
are made with the lower corners and the top of the strip. 
The roll mule is not used so extensively as the frame type, but it is very popular 
on the Illinois and some other rivers. It consists of a piece of canvas, tarpaulin, or 
heavy cloth cut according to the size and shape desired. An iron rod is attached to the 
bottom of the mule and a wooden bar at the top. To the four corners of the cloth small 
lines are secured for the purpose of adjusting the mule to the boat. This form of mule 
has the advantage over the other in that when not needed as a sail it can be rolled up 
and put out of the way in the boat or used as a tent against unfavorable weather. It is 
