770 BULLETIN OF THE BUREAU OF FISHERIES. 



It should be said here that this construction was adopted to save rebuilding 

 the floats which had formerly held canvas bags, in which case the low shaft 

 beam was not in the way. In the case of new construction, the shaft beams 

 should be high enough to escape the box when the latter is raised out of the 

 water (fig. 5, pi. xcii). 



The boxes are buoyant and have to be forced down into position, where 

 they are held fast by two planks across the top at the end of the box (fig. 4, pi. xci) . 

 The planks are mortised into the corner posts before referred to, so as to prevent 

 lateral movement, and are fastened down to the beams of the float by heavy 

 adjustable cleats secured by bolts (fig. 4, pi. xci; fig. 9, 10, pi. xciv). The 

 boxes are painted inside and out. 



When a box is to be raised, the cleats are loosened, the planks removed, 

 and ropes from the drums of a transportable windlass are hooked into the ring- 

 bolts of the bottom corners (fig. 9 to 12). The doors are then opened and 

 the hand windlass put into operation. One man has raised a box alone in 

 fifteen minutes, and two men in five minutes. These boxes, the windlass, and 

 many other things were designed and constructed by the superintendent, 

 Mr. E. W. Barnes. 



Propellers. — The size and shape of propeller blades found to be most satis- 

 factory vary according to the requirements of different fry. The form of those 

 most used for lobster fry is shown in figures 6, plate xcii; 8, plate xciii; and 

 18, plate xcviii. They consist of two wooden blades, each 4 feet 2 inches long 

 and 8 inches wide at the base, tapered to 5 inches at the apex, and painted 

 all over. Along the middle line the thickness is about i % inches, but from this 

 to either edge is a long bevel which leaves about jA inch at the edge (fig. 8). 

 Each blade is fastened with, iron straps to a piece of galvanized gas pipe, which 

 is screwed into a four- way cross coupling (fig. 1 8) . The latter admits also the 

 vertical gas-pipe shaft running upward toward the gears and a short vertical 

 steel shaft below which sets into a socket consisting of a short piece of large 

 gas pipe fastened to the bottom of the car by a flange. This serves as a lower 

 bearing or guard to the propeller shaft (fig. 18). 



The upper part of the propeller shaft is continued by means of couplings 

 through the longitudinal shaft beam and carries a mitered gear at the top (fig. 14, 

 pi. xcvi). In order easily to disconnect and take out the propeller a heavy iron 

 sleeve coupling is inserted into the propeller shaft. The two pieces of the latter 

 are held into the sleeve coupling by set screws (fig. 19, pi. xcix). As the set 

 screws would be too heavy for galvanized piping, the lower part of the pro- 

 peller shaft is continued upward by means of a piece of ordinary cold-rolled 

 steel shafting (fig. 19). This is more easily shown in the figures than described. 



Driving shafts and gears. — The gear on the top of the vertical propeller shaft 

 engages a similar gear with half the number of teeth on the longitudinal driving 



