 is the Mariner's Compass Rectified with Tables by Andrew Wakeley, a mathematician published in London in 1787. The reason we are looking at this book is because it contains a volval, which is an example of the earliest type of movable feature in books originally seen in medieval manuscripts. This of course is a printed book, but here you can see how the circles spin, and sometimes you'll see more layers containing different types of information. These are directions. Again, this is the Mariner's Compass Rectified, so it's a navigational text, and this tool, this volval, would have been one of the ways that Mariner's could calculate perhaps when the sun would rise and set where the stars were supposed to be or constellations at any particular given date in the calendar.