GERBER METHOD. 231 



The machine is fitted with the " Rapid " gearing, and has 

 plain bearings ; this causes continual driving to be necessary. 

 The machines cannot be left to run alone. 



None of the methods of driving the Gaertner-Hugershofi 

 machine are satisfactory. The catgut requires a strong pull 

 and is liable to soon wear out, if the metal end comes off ; if it 

 is required to rotate a second time, the machine must be stopped. 



The " Excelsior " gearing has a weak point in the spring, 

 which breaks and is difficult to repair ; the strap also sometimes 

 breaks, and cannot be replaced without some trouble. 



The " Rapid " gearing makes an unpleasant noise, and a great 

 deal of the power employed to drive the machine is wasted in 

 friction. 



It is far better to discard the methods of driving sold with 

 the machine and to employ a yard of blind cord (of the best 

 quality), one end of which is fixed into a wooden handle. This 

 is given one or two complete turns round the spindle ; the handle 

 is held in the right hand and the loose end in the left. The cord 

 is pulled with the right hand, just sufficient tension being kept 

 on the end with the left to make it bite. At the end of the 

 stroke, the left hand is brought up near the machine to loosen 

 the cord round the spindle, otherwise there is danger of the cord 

 winding up. 



The cord is now pulled back with the left hand keeping it 

 quite loose — i.e., letting the right hand go back quite freely. 

 The pulling with the right hand is repeated, and continued till 

 the speed is high enough. 



It is advisable to stop up the hole in the spindle, as it causes 

 the cord to wear. >Should the cord wear out and break, it can 

 easily be replaced at an infinitesimal cost. This method of 

 driving wa.s worked out in the author's laboratory by Boseley 

 and Rosier. 



The Lister Machine. — This has practically the same form 

 as the (iaertner-Hugershoif machine, but does not include the 

 '■ Excelsior " or " Rapid " gearings, which are covered by patents. 

 The frame is of different construction, and is S-shaped. Round 

 the spindle a small brass pulley is fixed * (in the i-t-bottle 

 machine a ratchet is added), and it is driven by a string wound 

 ronnd this by Boseley and Rosier's method, which, however, 

 was independently applied by Lister. 



The 2-bottle machine has the arms hinged, and clamped in 

 place by a screw, instead of having them in one piece ; it is 

 more easily portable. 



* In practice it is better to take oflf this pulley, stop up the hole, and 

 drive on the .ipiadle direct. The machines have also been made without 

 the puUey. 



