J. M. Blake— Method of Ruling Used by Nobert. 147 



Art. XII. — On the Possible Method of Ruling Used by 

 Nobert ; by John M. Blake. 



Nobert's ruled test-lines at one time were the subject of 

 much interest and discussion. They were regarded as marvels 

 of mechanical skill. The rulings designed and used as a test 

 of the performance of microscopic objectives were looked upon 

 as the most wonderful of his productions. 



It has been stated that after his death, an investigation of 

 his apparatus did not reveal his method of work. Possibly, 

 the apparatus which he actually used appeared to the investi- 

 gator so crude, and so far from what preconceived notions of 

 what such an apparatus shoidd be, that it was passed by as 

 unworthy of notice. 



The late William A. Rogers of Cambridge, Mass., devoted 

 much time and thought to the shaping of diamond points and 

 edges for ruling purposes, and had much success in ruling fine 

 and close lines. He took a great interest in what had been 

 done by Nobert, and made measurements of the latter's bands 

 of lines. Mr. Rogers! observations were published in the 

 "Proceedings of the American Academy of Arts and Sciences.*' 



At that time the writer was interested in Mr. Rogers' work 

 and it struck him forcibly that Nobert's bands could not have 

 been ruled on a machine like that used by Rogers. Quite a 

 different principle must have been employed. The writer went 

 so far as to plan out an apparatus involving the supposed prin- 

 ciple. This apparatus he hoped sometime to make and put to 

 the test. Its main features will be described, for we will 

 assume that some interest in these rulings still remains and 

 that no better explanation of a method of ruling such bands of 

 lines has yet been published. 



The proposed method dispenses with all sliding ways, joints, 

 and screws. The ruling point is to be held by a light spring- 

 bar, its motions controlled by electro-magnets; and the spacing 

 of the lines accomplished by change of temperature of bars of 

 dissimilar metals at measured time-intervals. 



In carrying out these conditions, a chronograph cylinder 

 would be used with contact points suitably disposed on its sur- 

 face. Provision would be made for heat storage in a medium 

 surrounding the machine. This apparatus would be placed in 

 a room that could be kept at a constant temperature. 



With this much provided, a preliminary trial of the ruling 

 apparatus would be made, and a line ruled at each revolution 

 of the chronograph cylinder during the fall in temperature. 

 These preliminary lines would be expected to diminish in dis- 



