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Maker, James Arthur. New York, USA, 1901, serial number 1 of 7. Astronomical regulator with unique tri-dial design, Graham deadbeat escapement with Wagner rocking frame, 60-second remontoire, one second compensated pendulum, wheels and frame fabricated from bronze. Arthur made seven of these, this being the first and having a dedication plate in honor of his son Daniel Arthur, dated June 13, 1901. Three are known to survive . Case dimensions 17.5"w x 81"h x 12"d.

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The drive weight is compounded substituting a conventional pulley with a sphere, nested into the weight shell. Pendulum compensation makes use of what may be a unique application of aluminum and steel. The external steel pendulum tube is perforated, allowing the change in air temperature to affect the internal pendulum parts faster and compensation to be made more efficiently; originally employed by Edward Dent in the 18th century and commonly known as the "tin whistle" design due to the look of the perforations which often were round holes.

The dial work is one of the more unique features of this clock. All astronomical clock dials have separate indications for the seconds, minutes and hours. Usually this is all accomplished with three dial hands on three sub-dials located on one overall dial plate. This clock uses three individual dial rings forming an equilateral triangle to offer both a visually striking contrast to a standard dial arrangement and to allow the triangular-shaped skeleton movement behind them to be seen. The dial rings are not of a conventional, flat design, but are a three-dimensional concave shape and each has a different numeral style to readily distinguish amongst them. Arthur used large diameter wheels that featured a wide variety of spoke numbers; from four, to six, eight and even a wheel with ten spokes.



The first photo is of James Arthur at age 67. He wrote a book about his horological interests in 1909. His clock is featured in the third illustration.

James Arthur was born February 26, 1842, of Scottish parents at Crosscandley, Ireland. While he was still a child the family moved to Glasgow where he attended the technical school and trained in mechanics, metal and woodwork. At this early age he took an interest in horology and made sundials and started restoring and collecting clocks and watches. In November 1871 he came to the USA. His wife and the three older children followed in 1872. James Arthur was a skilled mechanic with knowledge of machinery and fine construction. Fourteen years after coming to the USA he established the Arthur Machine Works at 188-190 Front Street, New York, for the manufacture and repair of machinery and providing mechanical models for inventors and gear designs for the nascent auto industry

He was a committed collector, who also produced a number of clocks of which one design, constructed in 1901, is worthy of consideration as a precision time piece. It is his astro-configured, three dial, one-minute remontoire regulator illustrated here. 

The predominant shape of the movement is that of an equilateral triangle. The great wheel has 144 teeth, the second wheel has 80, and the pinion has 40. The hour wheel and the fourth wheel have 120 teeth and the pinions have 24. The idler wheel and the remontoire have 120 teeth and the escape wheel has 30 and a 15 leaf pinion. The escapement is graham dead beat with flint-hard pallets. 

Arthur experimented extensively with aluminum using it for pallets and wheels. His experiments met with little success. The material was relatively new and absent of the appropriate alloying which would retain the light weight, yet add the requisite hardness for such application. However, he used aluminum effectively for pendulum compensation in this three-dial remontoire regulator. The pendulum has steel side roods. The steel center tube, perforated to facilitate rapid response to temperature change, encases an aluminum rod which expands or contracts in opposition to the steel.


Arthur used involute gearing, first animation, which provides a constant velocity ratio and is not as sensitive to minor depthing variations. As with epicycloidal teeth, second animation, the action takes place after the line of centers. Curiously, Arthur cut his teeth ten percent deeper and sized the pinions one-quarter diametral pitch smaller, but cut them to the regular depth . The meshing is somewhat shallow which would produce problematic backlash in a fast moving train which, of course, does not to clock movements. However, in Arthur's clock train, the space, resulting from this depthing, keeps dirt of dust from getting trapped between the teeth. The plates are made of gun metal and the clock runs for eight and one-half days. .

1. In addition to this example, one is in a private collection on the East coast of the USA and one example belongs to the great granddaughter of Arthur's other son John Forbes Arthur and two are in the collection of the National Association of Watch and Clock Collectors (NAWCC) Museum in Columbia, PA.

2. James Arthur, Machinery, (November 1901), pp. 70-73.

3. Derek Roberts, Precision Pendulum Clocks, article by Donald Saff, pp.206. 

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