London Polaris Equinoctial Sundial

This  London Polaris Equinoctial Sundial by Frank Morrison. American made. Patent No. 2559.

The dial appears to be German silver with all other parts of brass. The dial sits on central post and with a North pointer at base. The device has two thumbscrews and is designed to be mounted on a post. The lower thumbscrew is used to lock the device so the needle points North and the upper thumb screw allows dial plate to be set to the proper latitude by tilting the dial. The semi-circular latitude ring is marked in 1° increments from 0 to 90 S. latitude and from 90° to 0° N. latitude.

The base is signed London Polaris Frank Morrison, Cleveland O. Patent No. 2559. 

The unsigned dial plate is engraved in 1° increments from 0° at North to 180° at South , then reducing back to 0° at North.  The eastern quadrant is divided into 12 sectors with Roman numerals and marked P.M. The western sector is also subtended with 12 sections and marked A.M. The hour markings are further divided in to thirds, or 20 minutes each.

The alidade consists of rotating brass arm mounted above the dial plate, and on each end are attached sighting vanes. The vane with the sighting wire has a slider which adjusts vertically. The right leg of the vane It is inscribed with degree marks up and down 25° from zero. The top of the vane is marked “ DECLINATION”.  The left leg of the vane carries the inscriptions  “SAME NAME AS LAT” as a slider move upwards, and “ CONTRARY NAME TO LAT”  as the slider is moved down.

The opposite vein on the Adelaide is inscribed with cruciform slots on a curved brass plate.  This plate is painted white on the inside surface and unpainted on the outside surface. Below this vein is a central needle which indicates the direction of the alidade.

The small size and folding nature of the alidade indicate it was probably used for travel and exploration. I would guess this was probably a terrestrial instrument as opposed to a nautical device.  Although it’s possible, this could have been mounted above the magnetic compass, it might also have been mounted on a flat surface and oriented north. 

Weight: 6 lbs. 4.6 oz. 

Dimensions: 9” diameter, 13” tall unfolded