876 EEPORT— 1892. 



of a ton at a time upon a trolly, and are contained in bags of half a hundredweight 

 each. Four of these bags are placed upon the cage of a lift, which raises them 

 automatically to such a position that two attendants above can remove them to 

 Hat tables, one on each side, upon v^bich they are emptied, and the coins, being 

 spread out, are fed down by hand to a slanting table, where they lie, one coin 

 deep, with their rims touching, a iiat superimposed cover preventing the possibility 

 of one coin overlapping another. 



From this table they are allowed to move out one at a time, along a groove or 

 channel, the width of one coin, and, being inclined at an angle of 45°, they pass by 

 gravity between the edges of two driving wheels, which are actuated by an electro- 

 motor, and which grip the coins as they arrive, forcing them witli considerable 

 pressure along the groove. Each coin thus pushes the one in front of it, until they 

 reacli a wheel, which is so arranged thit its teeth fit into the spaces between the 

 coins, and which is driven round by the coins as they pass it. This is called the 

 counting wheel, since it shows by its revolutions the number of coins that have 

 been delivered. Wheels with teeth of diHerent pitch can be substituted for count- 

 in"' coins of different sizes. 



The coins having thus registered themselves fall through a tube into a bag 

 placed at a convenient height from the tioor. 



The counting wheel, above mentioned, i^ allowed to revolve until it has de- 

 livered a certain number of coins ; it is then stopped automatically, and at the same 

 instant the driving wheels, higher up in the groove, are released I'roni acting upon 

 the coins, and cannot again bo brought into action until a lever is moved by an 

 attendant. In the meantime the bag containing 1,"200 pence, or 5/. worth, has been 

 removed, and a fresh bag substituted. 



The principal advantage of this method of counting is that an intermittent 

 supply of coins does not atlect the accuracy of the count, since if the supply of 

 coins to the driving wheels ceases from any cause the only result is that the wheel 

 stops, and, until a fresh coin starts it, it remains stationary. 



The machine at the Mint is capable of counting pence, halfpence, piastres, 

 half-piastres, and Hong Kong cents, and it counts on an average over two million 

 coins per month without error. 



7. Antifriction Materials for Bearings used without Ltihrlcants. 

 By KiLLiNGWORTH Hedges, M.hist.C.E. 



The use of oil as a lubricant in machines is to separate the rubbing parts so as 

 to prevent the interlocking of the metallic particles of the bearings. Heavy 

 lubricants effect this separation better than those of a more limpid kind, but 

 absorb more power. 



The actual composition of the metal forming the bearing makes little difference, 

 provided oil in sufficient quantity can be introduced. This is proved by the little 

 wear shown on the cast-iron bearings used for shafting. The use of oil involves 

 loss of power when the pressure per square inch on the bearing is very low, 

 Professor Coleman Sellers considering that even up to 50 lb. on the square inch 

 the viscidity of the unguent acts as a sensible retardant. Dry bearings, or those 

 in which no lubricant is required, although only recently introduced into modern 

 work, were probably the original type of bearings, as they were used in the 

 Eoman mill-stones found at Pompeii ' and up to the present day for all the bear- 

 ings in the Nubian water-wheels employed for irrigation work in Egypt. In the 

 present time bearings of stone, adamas, and glass have been tried, also a variety 

 of mixtures of plumbago, but none was so successful as the solid form of graphite 

 bearing, which was often employed by millWrights for the footsteps of shafts. A 

 modification has recently been reintroduced into the United States, where the 

 ktest form of dry bearing is composed of plumbago mixed with wood fibre and 

 pressed when in a moist condition into suitable moulds. This bearing has been 

 highly praised by the Committee of the Franklin Institute, who state that ' dry 



' Clarke, Pompeii, vol. ii. p. 136. 



