[Illustration: FIG. 1.--TRAVELER'S SUN DIAL.]

The accessories of the instrument are as follows: A ring with a pivot
for suspending the meridian circle, and the position of which, given
by a division in degrees marked upon this circle, must correspond with
the latitude of the place; two stops serving to fix the position of
the equator circle; finally the latitude of various cities. The
instrument was constructed at Paris, by Butterfield, probably in the
last quarter of the eighteenth century.

The second instrument, which is of the same nature as the cubical sun
dial--that is to say, with horary angle--is, unlike the latter, a true
trinket, as interesting as a work of art as it is as an astronomical
instrument. It is a little mandolin of gilded brass, and is shown of
actual size in Fig. 2. The cover, which is held by a hook, may be
placed in a vertical position, in which it is held by a second hook.
It bears in the interior the date 1612. This is the only explicit
historic datum that this little masterpiece reveals to us. Its maker,
who was certainly an artist, and, as we shall see, also a man of
science, had the modesty not to inscribe his name in it.

[Illustration: FIG. 2.--SUN DIAL IN THE FORM OF A MANDOLIN,
CONSTRUCTED IN 1612.]

No. 2 of Fig. 3 represents the instrument open. It rests upon the tail
piece and neck of the mandolin. The cover is exactly vertical. The
bottom of the mandolin is closed by a horizontal silver plate,
beneath which is soldered the box of a compass designed to put the
instrument in the meridian, and carrying upon its face an arrow and