130 SUMMARY OF CURRENT RESEARCHES RELATING TO 



The frame A (fig. 31) is made of cast iron, and is screwed down to- 

 the bench by four screws ; but it may, if preferred, be merely fastened 

 by clamps. On the upper portion of A, at a height of 6^ in. above the 

 table, two parallel rails B are fixed, and upon these, which are 9^ in. 

 long, the razor-carriage C travels. The process of fitting the razor- 

 carriage has been adopted by Prof. Delepine after many trials, and is 

 that employed for the saddle of the best American lathes. On one 

 side the rail has a V-shaped depression, the razor carriage being pro- 

 vided with a similar projection along its entire length to fit into it. 

 The bottom of this groove is cut away so that, even when the sides have 

 been somewhat worn with constant use, the V-shaped projection still 

 rests evenly on its two sides and does not touch the groove with its- 

 point. On the opposite side the carriage has a perfectly flat surface 

 which slides on a similarly flat rail ; thus the only points at which the 

 carriage touches the rails are the two edges of the V on one side and 

 the fiat surface of the rail on the other. The carriage overhangs the 

 rails by both side and under pieces ; the latter prevent it from being 

 lifted off the stand at any point of stroke ; but as these are not made 

 to fit they do not interfere with the perfect sliding of the carriage. 

 The carriage is made of one solid piece of gun-metal, and is pushed 

 backwards and drawn forwards by means of the upper portion, which 

 is in the form of a handle ; its heavy weight and the pressure of the 

 operator's hand hold it firmly on the rails. 



The razor-holder D, with its two jaws, is really an adjustable portion 

 of the razor- carriage, and is made of one solid gun-metal casting ; this 

 is necessary to ensure the rigid holding of the razor E by the four set- 

 screws F, two of which clamp the razor down on its carrier, and the 

 other two clamp it from behind. The razor can be adjusted at various 

 angles by means of the serrated movable piece G, which is pressed 

 against the carrier D by means of the thumb-screw H. Thus, if it is 

 necessary for the razor to be at a steep angle to the object, the carrier 

 D is tilted upwards and clamped with its edge in the top groove of the 

 piece G against the two screws I on the carriage. The razor-carrier D 

 can be made in such a manner that the knife may be set at an oblique 

 angle if specially ordered. These valuable adjustments in no way 

 decrease the rigidity of the razor. 



In the right-hand side of the knife-carriage is a dovetailed slot in 

 which there slides a projecting piece K terminating in a pin, which at the 

 return of each stroke impinges against a lever L, and this, in its turn, 

 transmits the motion to the ratchet wheel M. The scale on the side of the 

 carriage indicates the number of ratchet teeth moved at each stroke of 

 the lever, and the projecting piece is clamped against the desired number. 

 The scale extends to twenty ; there are 250 teeth on the circumference 

 of the ratchet wheel, and one complete revolution raises a micrometer 

 screw through half a millimetre ; thus one tooth represents a raising 

 of the object to the extent of 2 /a. This screw presses against the pro- 

 jection O of the dovetailed rising slide P, and by this means the 

 raising and lowering motion of the object is attained. The lever L is 

 brought back after each movement by the spring N. It will be noted 

 that the object is only raised after the section has been cut and the 

 knife withdrawn. The dovetailed rising slide P, with its projection 0, 



