Henricus Harpur / Londini. A rare pre balance spring English silver pair case Astronomical verge watch with year calendar indicating date, month, sign of the Zodiac and time of sunrise with further indications for day of the week, and the age and aspect of the moon with the corresponding time of moonrise.
Round pre-balance spring movement with egyptian pillars, verge escapement with four wheel train, fusee with gut line and regulation by means of [restored] tangent screw set up to the mainspring arbor; floral pierced cock secured to the backplate by means of a screw.
Matted gilt brass dial plate with two subsidiary silver dials and two groups of apertures between them; the plate further chased with cherubs pointing to the several apertures.
The upper subsidiary dial is a calendar consisting of a fixed outer date ring enclosing a rotating disc carrying a blued steel pointer to indicate the date on the ring. The center of this disc is engraved with sectors for each month and the corresponding sign of the Zodiac. Each sector also indicates the Julian day of the month on which the Sun enters each sign and, in addition, the average hour of sunrise for each month. To indicate the current month, a blued steel hand moves independently over the disc.
The lower subsidiary hour dial has a roman chapter ring enclosing an engraved scene of a riverbank with a town in the distance. There is a single blued steel hand.
The apertures between the dials each reveal a portion of a silver disc beneath. The indications are:
1. The day of the week and its ruling deity;
2. A set of three apertures positioned to show the age and aspect of the Moon and the time of moonrise.
There are setting squares adjacent the apertures.
The calendar work is a self contained unit pinned by means of three feet to the top plate of the movement. All the wheel work is fitted into recesses within the calendar plate. A six leaf lantern pinon on the fusee arbor engages the hour wheel [30 teeth] which, in turn, has a lantern pinion of four leaves driving the day of the week wheel [56 teeth]. The 13-leaf pinon on the day wheel engages all three remaining wheels. The first of these is a silver moon disc [59 teeth] engraved with the figure of the moon and concentric rings of numerals for its age and time of rising. Finally, two superimposed wheels [60 & 62 teeth] carry, respectively, the Zodiac disc and month hand. These latter two wheels are held together by tension washers which permit them to slip past each other and move at different rates causing the hand to progress through the month sectors engraved on the disc.
The cases are silver and plain except for the shutter to the winding aperture on the inner case. The pendant has a loose ring. Two pairs of steel springs on the edge of the calendar plate secure and release the movement from the case.
55mm diam. of outer case