#volvelle — Public Fediverse posts

Another #volvelle from my collection, The Planetary Hour Dial from The Simplex Publishing Company, ©1910. It "works" like this -- find your day of the week, set it to the appropriate month, then line up your approximate latitude at the bottom of the slot. Then find the planetary symbol most appropriate for a chosen activity, & find the ideal time of day in the slot. (See alt text for more.)

"I don't believe in astrology; I'm a Sagittarius and we're skeptical." -- Arthur C. Clarke

#astronomy
James Ferguson's 'Luminarium', a very rare card #volvelle (~1760).
For any date, the volvelle provides the duration of the semi-diurnal arc, or half-length of the day, from which you can find the sunrise/sunset times (for London) by adding or substracting from noon.

If you know the age of the moon for a given date (from an almanach), scales B & C help you find the Moon's time of 'southing' (crossing the southern meridian), and also the average moorise/moonset times by adding or substracting from the southing.

My reproduction, from the printout I made, for latitudes 42 to 52°N.
It seems that the National Museums Scotland has a copy. From its description I guess it could be different from this one.

Here's a VERY Rare Book!
Dare I say.... a UNICORN?

#volvelle #interactive #popup
#NewberryLibrary #NewAcq