48 H. J. Grayson : 



thy rods upon which the carriage slides to and fro, is best seen in- 

 Plate IX. It consists of two identically shaped strong brackets 

 bolted to the bed, one on each side, which serve mainly to support 

 two rectangular steel bars grooved on their upper surfaces, through- 

 out their length, to the exact curvature of the two circular glass- 

 rods (29) which are ground perfectly straight and accurately 

 uniform. These rods rest in, or rather float upon, a viscous medium 

 (thick oil or vaseline) within the grooves of the two steel supports. 

 The glass rods can be slightly adjusted to secure parallelism, and 

 alignment, by means of the four screws (30 and 31). Such adjust- 

 ment is very slight, and made with only just sufficient pressure to- 

 prevent any longitudinal movement of the bars. 



The chief effect of thus supporting the glass rods is the complete- 

 suppression of any tremour or vibration during movement of the 

 diamond carriage over their surface. The surfaces themselves are 

 not only ground, but are semi-polished, so that they consist essen- 

 tially of innumerable minute facets, and when so prepared render 

 the use of any lubricant unnecessary. It was found that the use of 

 any lubricant would vary in its action, frequently introducing a 

 variable load or pull upon the carriage during the progress of a 

 ruling. 



The diamond bearing carriage is seen detached in the plan 

 (Plate VI.), and in various other aspects in the series of photo- 

 graphs illustrating the machine. It is a somewhat complicated 

 piece of m,echanism. Leaving to a later page its more detailed 

 description, the following outline of its principal parts and move- 

 menta will serve to make clear its general operation. The plan 

 shows the outline of the carriage as a rectangular framework, which 

 is built up of brass and steel parts (32, 33 and 34) supporting a 

 superframe (35) carrying all the adjustments for raising and low'er- 

 ing those parts which control the movements of the diamond ruling^ 

 point, situated at 40, during the operation of ruling a line. The 

 chief adjustment in elevation is effected by means of a central screw 

 (36) operating' the dovetailed slide near 35. This slide carries all 

 the parts 37-42. 



The lower frame comprises the two broad bars (34) immediately 

 over the glass guides (29). These bars are connected together by 

 means of two steel plates (32, 33). The lower faces of the bars form 

 rectangular grooves, and are fitted Avith boxwood linings adapted to 

 the curvature of the glass rods upon which the frame slides to and 

 fro. This motion is conununicated to the carriage from the eccen- 



