This is an Equatorial Sundial because the dial plate lies parallel with the equator and the gnomon is parallel with the earth’s axis. Immediately you can see that the sundial is imitating the earth by this arrangement. This style of sundial has the advantage that the adjustments for Apparent Local Time, Local Mean Time, Greenwich Mean Time, British Summer Time, can easily be made by rotating the dial plate that is free to turn on the gnomon and is secured in a slot in the base. Since the sun is north of the equator for half the year and south for the rest the dial is read in the summer from the top and in the winter from the bottom.
The inscription is part Andrew Marvell’s poem “To his coy mistress.”