Fig. 9
The east and west vertical dials are made something like the equatorial horizontal dial, with a rectangular style. The same scale is required for making the line of hours, the lines of which are regulated in length by the height of the style. Make the plate about eighteen inches long and twelve inches wide, and draw the double lines which in these dials represent the six-o’clock line, as in Figs. 7 and 8. These double lines are drawn, making an angle with the lower edge of dial-plate equal to the latitude of the place. The style is cut rectangular, with the long sides equal to the double six o’clock lines, and the short sides two inches long. Draw the scale making O A and O B two inches long, and mark the hour line. Before the points on the hour line can be marked in on the dial-plate, a plan ([Fig. 9]) must be made. Draw on a large piece of paper a plan of either dial-plate, and mark in the double lines. Through these draw the line A B perpendicular to them as in [Fig. 9]. On this line, on each side of the double lines, mark the points on the hour line, and through these points draw lines parallel to the double lines, and letting them cut the sides of the plan of the dial-plate. The points where the lines cut it can be transferred to the dial-plate with a pair of compasses, and the hour lines drawn in parallel to the six-o’clock line. The style must be fixed in its place, and will be parallel to the axis of the earth when the dial is fixed up with the long sides quite horizontal. The east dial is marked as in [Fig. 7], and the west as in [Fig. 8], if for the northern hemisphere. For the southern, the west dial would take the place of the east, and the east, the place of the west with the numbering reversed.
There are several other kinds of sundials, which may be used for any degree of latitude, a few of which I will describe.
The first of these is the globular ([Fig. 10]). This is a white globe (any size), supported on an axis which is fixed in a position parallel to the axis of the earth (or making an angle with the horizon equal to the latitude of the place, and pointing due north or south), in which position the globe is acted on by the sun exactly as the earth is. The globe is divided into twenty-four equal parts by lines running from pole to pole, and has an equator drawn around it, on which the hours are marked from 1 to 12 twice over. The axis is fixed in a stand so that one of the six-o’clock lines is in the zenith. The time is indicated by the edge of the shaded part (caused by the sun illuminating one-half of the globe, leaving the other in shade) passing over the hour lines. An ordinary globe answers very well for this dial, if it is rectified for the latitude, and placed so that the brass meridian is directed north and south.
Fig. 10
Fig. 11
[Fig. 11] is another pattern; it is basin-shaped, and is made of a hollow hemisphere of metal, whitened inside, and has the inside divided into twelve equal parts by lines running from pole to pole, which are numbered on the equator from 6 to 6. A wire is stretched from pole to serve as the style, which casts a shadow on the line corresponding to the hour. The position of this dial is the same, as regards the axis of the earth, as [Fig. 10].
