New Engine for Kullmj. 49 



trie drive (52) and transmitted to the frame through the driving rod 

 (44). A second and smaller driving rod, not shown in the plan, 

 lies immediately under 44, and is so adjusted as to move in the same 

 direction, but slightly ahead of 44, thus raising or lowering the 

 ruling point in advance of any movement of the frame by 44. 



The sequence of movements in the ruling of a line is as follows : — 

 The diamond is first lowered into contact with the surface of the 

 plate to be ruled. This is effected by the falling of a bell-crank 

 lever due to the withdrawal of the rod underlying 44. The rod (44) 

 then draws the carriage slowly forward, through the interval deter- 

 mined by the position of the crank (53), and the line is completed. 

 The first return movement, due to the revolution of 53, raises the 

 diamond, through the lifting of the bell crank about .02 inch, above 

 tlie ruled plate before any movement of the carriage on its ways can 

 occur. The moment the diamond is clear the return journey of the 

 carriage commences, and continues to the starting point of the next 

 line; the diamond remaining suspended both during the return 

 journey of the carriage and feed of the ratchet wheel which occur 

 at the same time. The several movements ars so timed and adjusted 

 as to permit the longest stationary interval to be precedent to the 

 lowering of the diamond for each fresh line. 



The time occupied in the ruling of a single line may vary from 

 5 to 10 seconds, according to the length of the line ruled, and 

 degree of accuracy required. The slowest rate named, calls for some 

 check upon the descent of the diamond point at the start of each 

 fresh line. An unchecked fall would speedily ruin the delicate cut- 

 ting edge of any diamond suited to this work, hence its fall has to 

 be so graduated as to avoid any sort of shock or blow. This is 

 effected through the agency of three plungers and dash cells, the 

 latter containing a fairly thick oil. The plungers are situated at 

 42 and 42a. The lines are also, by this means, freed from the 

 effects of undulatory vibration of the diamond in a vertical plane. 



This brief reference to the action and control of the diamond 

 during the cutting of a series of lines might properly lead to a 

 description of the form of diamond, best suited to this work, at this 

 stage. A careful study of the cutting action of a diamond for 

 ruling lines of such extreme tenuity and perfection as are required 

 for diffraction gratings, is of the very first importance. The 

 amount of Avork required of a diamond in the cutting of even a 

 medium-sized grating is equal to the cutitng of a single continuous 

 line of over a mile in length. This line, or rather series of lines, 



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