3G ANNUAL OF SCIENTIFIC DISCOVERY. 



tile and armed, that arc retarded by the heating and wearing in the stuffing 

 boxes and bearings of their shafts. 



It appears to the writer that the causes for this can be easily explained, 

 and the effects modified if not prevented. The heating of the bearings 

 inside a vessel results from one cause : the wear and heat in the stuffing box. 

 and outside journals result from totally different causes. 



In most cases the machinery of a steamship is placed in the centre of the 

 vessel, and thence motion is carried to the propeller blades by a long shaft 

 rigidly connected. If the frame of the vessel springs at all by the mo; ion 

 of the sea, the shaft is thrown out of line, and must consequently heat. T<; 

 remedy this the shaft should be allowed some play in the couplings where 

 the lengths of the shaft are joined together. 



But it is the wearing of the journals and bearings outside the vessel that 

 is most prejudicial, most frequent, and most difficult of repair. One cause 

 of this wear is that the blades are not made smooth and not balanced, so 

 that the centre of rotation and the centre of gravity do not coincide. No 

 machinery in revolving works well under these circumstances. 



But the most important disturbing cause is the following. The propeller 

 blades of a vessel on leaving port are set in motion in a plane at right angles 

 to the vessel's keel. The propeller blades tend to "persist" in this plane, 

 and the greater their momentum the greater their resistance to any cause 

 tending to draw them from this plane. But the motion of the vessel is a 

 constant disturbing cause, and in resisting the motion of the vessel the re- 

 volving propeller presses with great force on the bearings. 



Suppose, as in some vessels, the propeller (blades and hub) to weigh fif- 

 teen tons. Propellers of this size have their centres of oscillation moved at 

 the rate of thirty-six feet per second when in full action. We have then a 

 weight of fifteen tons moving at thirty six feet per second, to be deflected 

 from its line of action whenever the vessel rises or falls. The wear caused 

 by this action has been attempted to be overcome by putting wooden linings 

 in bearings ; how far successfully has yet to be shown. 



It would undoubtedly be better to remove the cause than to remedy 

 the effects. It seems to the writer that the cause may be easily removed by 

 simply so arranging the propeller blades (or the frame in which they are 

 mounted), that the propeller blades can keep in the original plane of rota- 

 tion however the vessel may move in a sea way. The plans for effecting this 

 are not easily explained without drawings. But means of so arranging the 

 propeller blades that they will keep vertical however the vessel may move 

 will occur to most persons acquainted with machinery. 



MASKEL'S SLIDING KEEL. 



This invention consists of a plate of iron, or other suitable metal, which 

 is moved vertically in a recess made for it in the keel. A link at each end 

 attaches the plate to the keel, provision being made by slitting the pin-holes 

 of the links, to allow for the raising or lowering of the plate, which is 

 accomplished by racks and pinions, or other suitable machinery, worked on 

 the vessel's decks, the attaching rods passing through water-tight tubes ex- 



