118 SCIENTIFIC AND TECHNICAL LABOURS TO 1850. 



itself and also for the alarum. The principle essen- 

 tially consisted in increasing, according to require- 

 ment, the stroke of the well-known Neef hammer by 

 the insertion of a moveable contact, the so - called 

 slide. My dial and type -printing telegraphs, depend- 

 ing on this principle, were distinguished from the 

 then well-known Wheatstone telegraphs by being auto- 

 matic machines, running isochronally with one another, 

 until one apparatus was mechanically stopped by the 

 depression of a key on the particular letter, where- 

 upon all the others likewise stopped at the same letter, 

 and this letter was printed off by the type - printer. 

 The description of these instruments, as of most of 

 my further inventions and improvements of telegraphic 

 conductors and apparatus down to the year 1850. is 

 contained in my "Memoire sur la tele grap hie electrique" 

 communicated to the Paris Academy. I content my- 

 self here with a concise summary of the most important 

 scientific and technical improvements, the priority of 

 which is secured to me by that publication: 



Introduction of the automatic break. of the electric 

 current at the end of every moA r ement of the armature 

 through a predetermined distance. Or one may put it 

 thus: increase of the movement of the Neef hammer 

 by a mechanism answering to the slide of the steam- 

 engine. All automatic electric alarums without clock 

 work and many other constructions rest on this 

 principle. 



Production of the synchronous action of two or 

 more electric machines by allowing a fresh impulse to 



