92 SEC. 3. MEASUREMENT. 



453. Keyless Watch, complete, with centre seconds and 

 going barrel. James Pooh $ Co. 



454. Ship Chronometer (2 day), complete. 



James Poole fy Co. 



455. Ship Chronometer (2 day). Movement reversed, to 

 show workmanship. James Poole $ Co. 



456. Chronometer Movement (2 day), as received from 

 the factories in Lancashire. James Poole fy Co. 



456a. Six Chronometers with rates from the Geneva Obser- 

 vatory, stating records of trials of the years 1875 and 1876. 



If. R. Ekegren, Geneva. 



No. 16,175, gold, open face, 21 lines, keyless. 

 No. 16,873, 18 



No. 16,144, 

 No. 16,534, 

 No. 16,576, 

 No. 16,525, 



Chronographs, 19 lines, keyless. 



hunter, 21 lines, keyless. 

 19 

 18 



457* Regulator Clock, filled with the Exhibitor's new patent 

 gravity escapement, having no upward locking, and which cannot 

 trip or slip teeth. Alfred John Higham. 



On the escape wheel there are two sets of teeth, one set longer than the 

 other ; the teeth of each set are arranged, and the pallets are formed and 

 placed, so that the shorter set of teeth only are used, except in case of acci- 

 dents, when the longer set come into action. This secondary locking entirely 

 prevents irregularity in the clock rate, but the clock can be allowed to run, if 

 desired to be so set to time, by removing two extra stops which are adjust- 

 able. The action of the escapement is ordinarily exactly the same as that of 

 the gravity escapements invented by Mr. Denison (Sir Edmund Beckett, 

 Bart.), and the secondary locking can be applied to those escapements. 



458. Regulator, with improved gravity escapement on the 

 Bloxamic principle, as arranged and patented by Mr. Higham ; 

 founded on the old pin-wheel escapement, and fitted with a gal- 

 vanic inteiTuptor for chronographical and other astronomical 

 purposes. Charles Frodsham fy Co. 



459. Marine Chronometer, fitted with a galvanic inter- 

 ruptor for chronographical and other astronomical purposes. 



Charles Frodsham fy Co. 



460. Apparatus for demonstrating the application of the 

 pendulum to the clock, at the same time serving for audibly indi- 

 cating the minutes. 



The Secondary Government School at Assen (Netherlands). 



This apparatus is constructed by C. H. Van. der Heyden, watchmaker, at 

 Assen (Netherlands), after deliberation with Dr. A. Van Hasselt, teacher at 



