OYSTERS AND METHODS OF OYSTER-CULTURE. 319 



account of the difficulty of cutting grass growing under water, he invented in 1885 

 and has since used a device which may be termed an aijuatic mowing machine. 

 The machine is rigged on a 8(iuare-ended scow 20 feet long by 8 feet wide. On the 

 forward end of the scow is suspended, by a framework, a double set of knives, each 

 set being similar to those of mowing machines used by agriculturists. The object 

 in having double knives is to enable the machine to cut when moving backward aa 

 well as when moving forward, thus avoiding the necessity of having to turn the 

 scow around when the end of the swath is reached. The knife bar is 12 feet long 

 and consequently cuts a swath 12 feet wide. The power of propelling the machine 

 is supplied by a 6-horsepower high-pressure condensing engine, which is located in 

 the middle of the scow. A line 1,000 feet in length is passed with three turns around 

 a winch head and drawn taut by an anchor at each end, placed a short distance 

 beyond the extreme boundaries of the area to be mowed. It is held in position by a 

 fair-leader or chock having a shive on each side similar to the shive of an ordinary 

 tackle block. The shives facilitate the passage of the line through the leader by 

 lessening the friction and correspondiuyly decrease the wear upon it. The leader 

 or chock is placed on the forward end of the scow, and not only serves to hold the 

 line in position, but also keeps the scow straight in its course. 



When the engine is started, the winch-head revolves, and the pressure of the line, 

 encircling it in three turns tightly drawn, forces the scow through the water. The 

 rate of speed at which it can be operated is 1,000 linear feet in 5 minutes, thus 

 enabling it to mow an area of 2,000 square feet or more per minute, or 1 acre in from 

 20 to 22 minutes, making allowance for time spent in moving anchors or otherwise 

 adjusting the machinery. 



When fitted for work, with coal and water, and manned with three men, including 

 an engineer, which is the number requisite to operate the machinery and attend to 

 shifting the anchors, the draft of the scow is about 8 inches of water. When the 

 * anchors have once been adj listed, several swaths can be mowed before they require to 

 be shifted over toward the uncut grass, as the line can not easily be drawn so taut — 

 nor does it need to be — as not to allow the scow to be moved (pushed with a pole) 

 sidewise for a short distance. When necessary, the anchors are shifted by the use of 

 a small boat. Thus the scow is guided back and fortli across the lot, cutting the 

 grass with equal facility in both the forward and backward movements. When the 

 grass is cut, it floats to the surface of the water and is carried away by the current. 

 The knives are set in motion by a vertical iron shaft which passes through a hori- 

 zontal cogged wheel. This wheel is geared to a pulley which is run by a belt from 

 the engine. The vertical shaft is so arranged as to slip up or down in order to gauge 

 the machine to any depth of water within the range of its capacity. The extreme 

 depth of water in which mowing can be successfully done, as it is now adjusted, is 

 about 8 feet. It could doubtless be so arranged as to operate in deeper water. 



If there are no obstacles in the way, the grass can be cut within 1 inch of the bottom. 

 If there are oysters on the ground, some allowance for that fact has to be made, 

 and while the grass can not be sheared so close to the bottom, it can be mowed 

 sufficiently close to the oysters to answer all practical purposes. The only thing 

 requisite is to mow it short enough to preclude the possibilitj' of any large quantity 

 of sediment settling in it and choking the oysters. This object is easily attained, as 

 grass a few inches long will not injure the oyster crop. It is when its length is 

 measured by feet and it is filled with sediment that it becomes dangerous. 



In the locality where this machine is used the water is about 6 feet deep. It 

 has been customary to mow the oyster-beds quite frequently, five or six times, 

 perhaps, during the growing season, from the first of May to the last of October. The 

 result has been that tracts of bottom that would have otherwise been worthless for 

 oyster-growing purposes have been converted into beds as productive as any in the 

 river. The coat of building a similar machine is estimated by Mr, Alien to be from 

 $450 to $500.* 



* Hall, Ansley, Rept. U. S. Fish Commission 1892, pp. 477 and 478. 



