R. Hopkins of two patents," in both of which half 

 rights were assigned to William D. Colt. Fatcni 

 165831, relates to a barrel arbor for watches. The 

 arbor will ix' seen (fig. 4) to consist of two parts, one 

 telescoped within the other and the composite arbor 

 B-C supported at each end by the irame of tlie watch. 

 The patent text limits itself to a bare description of 

 the arbor. In the light of what we have seen of the 

 shortcomings of the original model, however, the 

 patent drawings tell that much more had been accom- 

 plished on the general design of a more workable 

 rotary watch. 



\ square on arl)or C at the back of the watch permits 

 winding the main spring, which attaches to the 

 largest diameter of C, a ratchet or winding click being 

 supplied just under support F. The inner or front 

 part B of the composite arbor projects from the front 

 of the movement and re\()l\es at the speed of the 

 barrel arbor, which speed is not specified. Also, 

 looking at the perspective view, we see that while the 

 chronometer escapement has been retained, the 

 balance has been placed eccentrically to make room 

 for the center arbor. The balance now describes an 

 orbit around the center of revolution. No driving 

 train is shown, it being irrelevant to the patent, biu 

 there seems to be ample room for two intermediate 

 wheels and their pinions between the escape wheel 

 and the train cock boss, .seen at the upper right in the 

 perspective view of figure 4. Adding one more wheel 

 and pinion to the train would have the effect of 

 reducing the number of revolutions required of the 

 spring barrel. We have seen from examination of the 

 patent model of the Hopkins rotary that this was 

 necessary not only to reduce the number of turns of 

 the main spring and barrel but also to reduce the 

 force transmitted to the escapement. There seems 

 little reason from the foregoing oKserva lions and con- 

 siderations to doubt that these modifications had been 

 realized by the time of this patent. Again no dial gear- 

 ing is shown. If the need for special gearing existed 

 at this time it seems strange that it was not covered by 

 patent as was done in the later patent'" assigned 

 to William B. Fowlc. The only way to avoid special 

 gearing would be to revolve the barrel and train each 

 hour so that the minute hand could travel with ihem 

 as it travels with the center wheel in conventional 

 watches. Once this condition was set up, the usual 

 dial gearing would apply. 



Companion patent 165830 (see fig. 5) covers a 

 mechanism to prevent overljanking of the balance 

 wheel. |)rimarilv of a chronometer escapement. This, 

 ofcour.se, was aimed at making it possible to use the 

 escapement in connection with a mainspring of 

 greatly varying power. We have seen ihat this condi- 

 tion of imeven power existed in the first Ho|)kins 

 watch. \\ hile the condition was greatly improved in 

 the sect)n(l model (seen in fig. 4), it was surelv present 

 to some extent, as it is a.ssociated with every S|)ring. 

 Overbanking protection may well have continued to 

 be necessary, particularly if the gear ratio between 

 esca[)ement and l)arrel was low enough to permit 

 hourly rotation of the barrel. The features co\ered 

 by this patent were originally submitted as part of 

 what later became patent 165831. Examination of 

 the original manuscript patent file " shows that the 

 jwtent application was separated into two on the 



Figure 6. — Drawing from U. .S. P.vtent lygoig 

 showing Hopkins' device to prevent the tripping 

 of a chronometer escapement. 



suggestion of the patent examiner, who pointed oiu 

 that two distinct and separate mechanisius were 

 involved, either of which could be used without the 

 other. 



These two patents, which actually started out as one, 

 api^ear to represent the watch as it was when Hopkins 

 went to Waterbury, Clonnecticut. where he again met 

 Edward .\. Locke. They submitted this improved 

 w^atch model to the Benedict and Burnhani Manu- 

 facturing Co., which advised not manufacturing it 

 until it was further developed. Hopkins went with 

 his watch from there to Boston, where he conferred 

 with George Merrilt who. like l.ocke. was interested 



' U. S. patents 165830 and 165831, granted July 20, 1875. 

 '»U. S. patent 186838, January 30, 1877. 



" Patent file 165831, records of the Patent Office 

 National Archives, Washington, D. C. 



in the 



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BULLETIN 218: CONTRIBUTIONS FROM THE MUSEUM OK HISTORY AND TECHNOLOGY 



