the sun, is considered as a point, and therefore if a small sphere of glass be placed upon any part of the earth's surface so that its axis be parallel to the axis of the earth, and the sphere have such lines upon it, and such plans within it, as above described, it will show the hour of the day as truly as if it were placed at the earth's centre, and the shell of the earth were as transparent as glass. The diversity of the titles of sun-dials arises from the different situation of the planes, and the different figure of the surfaces whereon they are described, whence they are denominated equinoctial, horizontal, vertical, polar, erect, direct, declining, inclining, reclining, cylindrical, &c.

The Pocket Ring Dial.

All the before-mentioned time-measurers were up to a certain period non-portable, and in addition to the drawback of being unserviceable excepting when the weather was clear and the days bright were as useless for private purposes, as they were unadapted for the winter-time or for night. The next step was therefore a portable dial, but this was probably not invented until after a very long interval. The Dial of which the above is an illustration, was probably one of the earliest of portable time-keepers, the time being shown by means of a hole through which the light fell on the inside, which had an inner ring adaptable to the day and the month. Ring-dials of this description were in common use within the last century in this country, and were manufactured in large numbers at Sheffield when watches were too expensive to be generally attainable. Some of these Ring-dials were of superior construction, and were made by means of more than one ring to serve for different latitudes. As an example of a still greater advance in the manufacture of pocket dials, see the illustration on the next page.

The Dial consists of a thin silver plate properly divided and marked, and having a compass with glass cover sunk at one end of it. The Gnomon or style moves upon a hinge so as to allow of its lying flat upon the Dial while in the pocket, and thus rendering the instrument conveniently portable. The Gnomon itself is also susceptible of elevation or depression and the beak of the bird carved on a thin slip of silver at its side marks the exact extent of the Gnomon's elevation. This Dial is indubitably of French manufacture.

One would imagine that it was such a dial as this that Shakspeare had in his mind's eye when he wrote the well-known passage which he put into the mouth of Jaques, wherein that philosophic satirist describes his meeting with a fool in the forest.

Silver Pocket Dial (in the collection of the Honble Company of Clockmakers, London).

What the fool's dial was, has given rise to many conjectures, but there is no better authority perhaps on the subject than Mr Halliwell, from whose magnificent and elaborate folio we will make the following very interesting extract.

'The term dial appears to have been applied in Shakspeare's time to anything for measuring time in which the hours were marked, so that the allusion here may be either to a watch, or to a portable journey ring, or small dial. The expression "it is ten o'clock" is not decisive, as it may be considered to be used merely in the sense of the hour thus named. * * * A watch even is sometimes called a clock, * * * and it seems by no means unlikely that the common ring dial which has been in use for several centuries up to a comparatively recent period, should be the dial referred to in the text.'

Whatever may have been the shape of the dial which Jaques saw drawn from the fool's 'poke,' it is an undoubted fact that portable dials did serve the part of time-keepers, and were in their way valuable as such to those who had learnt how to use them. But the dial would not do the work of the watch in an age when people no longer travel by the waggon-load or with pack-horse, but are whirled fifty or sixty miles in that time and have to reckon their engagements not by the day, but by the minute. The world no longer 'wags' in jog-trot style, but speeds at steam-pressure and sends its messages by lightning-conductor; it consequently values its time more highly and measures it more carefully.

The Horologe which possibly next succeeded in date the invention of the Dial, was the Clepsydra or Water-Clock, the precise antiquity of which is however unknown.

The Clepsydra, or Water-Clock of the Greeks.

The Clepsydra is so named because the water escapes from it as it were by stealth, but in a regulated flow so as to permit of the lapse of time being computed thereby, even as by sand running through sand-glasses. The Clepsydra appears to have been at first used to limit the time during which persons were allowed to speak in the Athenian Courts of Justice; 'the first water,' says Æschines, 'being given to the accuser, the second to the accused, and the third to the judges,'—a special officer being appointed in the courts for the purpose of watching the Clepsydra and stopping it when any documents were read whereby the speaker was interrupted. The time, and consequently the water allowed, depended upon the importance of the case. This custom, says Phavorinus, was to prevent babbling, that such as spake should be brief in their speeches. Ctesibius of Alexandria, who lived about 245, invented a much improved water-clock, mentioned by Vitruvius and Athenæus. Another kind of Clepsydra consisted of a vessel of water having a hole in it through which the fluid gradually escaped; a miniature boat floated upon the water and descended as the water decreased, whilst an oar placed in the boat indicated the hour by pointing to certain line-marks on the side of the vessel. The hole through which the water dropped was made, we are told, through a pearl, because it was supposed that the action of the water upon the pearl would not, as upon other substances, enlarge the aperture, nor would the pearl, it was imagined, be choked by the adhesion of any