SUN-DIALS AND THEIR MOTTOES. 
O 
excavations at Herculaneum, a city overwhelmed by an eruption 
of Vesuvius, a.d. 79. It was most likely made very shortly 
before that date. A German dial (Fig. 2, p. 3) dated 1612 exactly 
illustrates the principle of this Herculaneum dial: the instrument 
is held up by its ring, the projecting arm being fixed opposite 
the space marked with the name of the month, and when the arm 
is pointed towards the sun its shadow gives the hour. On the 
back of this instrument is a “nocturnal” or night dial, about 
which I shall speak later on. 
This same method was adopted in the cylinder, a form of dial 
much used in Europe in the Middle Ages; it was mentioned in 
English manuscripts as early as the thirteenth century, and it is 
still used in the Pyrenees. In the cylinder dials the projecting 
arm is fixed in a kind of stopper, which has to be turned until the 
Fig. 4.— Brass Bing Dial. England. 
arm is over the proper month-space. One of the two cvlinder-dials 
exhibited (Fig. 3, p. 4) is English, about 1770, and the other was 
bought in the Pyrenees last year. The gilt brass disc made to 
resemble an astrolabe shows this type of dial in another shape; 
it was made about 1570 in Germany. 
Another form of dial, which in its action depends on the height 
of the sun above the horizon, is the ring-dial, in which a ray of 
sunlight is allowed to pass through a hole pierced in the side of 
the ring so as to fall on hour-lines engraved within the ring. 
1 am exhibiting two English ring-dials, one a silver finger-ring 
made about 1620, and the other (Fig. 4) a larger brass ring of 
about 1760. 
Many other devices were employed for telling the time from the 
sun s altitude, as will be seen from the gilt brass hanging dial and 
calendar, “ Hathaniell Torporley inventor,” 1593; the Gunter’s 
