I have recently been shown an interesting brass heliochronometer made by W. Homan of Glasgow according to his patent 18,568 of 1911. (I hope to receive a copy of the patent shortly.)
It is quite large, based on a 13 1/2" diameter hemisphere. It has two "gnomons", upright brackets carried on and perpendicular to a circular plate 11" diameter. The plate has, over an adjustable 15 degree arc at its edge, a scale divided in minutes, and can be rotated by hand against an outer fixed ring marked with hours from 1 to 12 twice. Each upright carries a half analemma, one for positive and the other for negative solar declination (summer and winter), and a slit - with in one case a small hole adding a nodus to the slit - to project light onto the half analemma on the other upright 7 7/8" (200 mm) away. It is set for a latitude (not adjustable) of about 7 degrees North, and a time difference from the local meridian of 5 minutes (added to the reading, so it was sited just over 1 degree West). This indicates it was made for use not in Britain but somewhere tropical, perhaps West Africa or Ceylon. Has anyone come across other example(s), or information about this device or its maker? Andrew James N 51 04' W 01 18' -
