of many hours, enabling the passengers to pass over large tracts of country. On one of these occasions, Mr. Blanchard, a noted operator, with a favourable wind, passed over from Dover to Calais, accompanied by another gentleman.

Many other persons exhibited balloons, of large dimensions, particularly in France and other parts of the continent, with various success. The people of that country have also successfully applied balloons to the examination of the state of the higher regions of the atmosphere; and also in their armies, to discover the dispositions and operations of an enemy's position and camp. In England they have been less attended to, perhaps owing at first to an unfortunate prejudice, and an idea thrown out, that they could not be turned to any useful purpose in life.

A representation of several different balloons, is exhibited in plate 19.

TELEGRAPHS.

A TELEGRAPH is a machine lately brought into use by the French nation, namely in the year 1793; being contrived to communicate words or signals, from one person to another, at a great distance, and in a very short time.

The object proposed is, to obtain an intelligible figurative language, to be distinguished at a distance, to avoid the obvious delay in the dispatch of orders or information by messengers.

On first reflection we find the practical modes of such distant communication must be confined to sound and vision, but chiefly the latter. Each of

these is in a great degree affected by the state of the atmosphere: as, independent of the wind's direction, the air is sometimes so far deprived of it elasticity, or whatever other quality the conveyance of sound depends on, that the heaviest ordnance is scarcely heard farther than the shot flies: and, on the other hand, in thick hazy weather, the largest objects become quite obscured at a short distance. No instrument therefore, designed for the purpose, can be perfect. We can only endeavour to diminish these defects as much as may be.

Some kind of distant signals must have been employed from the earliest antiquity. It seems the Romans had a method in their walled cities, either by a hollow formed in the masonry, or by tubes affixed to it, so to confine and augment sound, as to convey information to any part they wished; and in lofty houses it is now sometimes the custom to have a pipe, by way of speaking trumpet, to give orders from the upper apartments to the lower: by this mode of confining sound, its effect may be carried to a very great distance; but beyond a certain extent the sound, losing articulation, would only convey alarm, and not give directions.

Every city among the ancients had its watchtowers; and the castra stativa of the Romans had always some spot, elevated either by art or nature, from whence signals were given to the troops, cantoned or foraging in the neighbourhood. But they had probably not arrived at greater refinement than that, on seeing a certain signal, they were immediately to repair to their appointed stations.

A beacon, or bonfire made of the first inflammable materials that offered, as the most obvious, is perhaps the most ancient mode of general alarm, and

by being previously concerted, the number or point where the fires appeared might have its particular intelligence affixed. The same observations may be referred to the throwing up of rockets, whose number or the point from whence thrown may have its affixed signification.

Flags or ensigns, with their various devices, are of earliest invention, especially at sea; where, from the first idea, which was probably that of a vane to shew the direction of the wind, they have been long adopted as the distinguishing mark of nations, and are now so neatly combined by the ingenuity of a great naval commander, that by his system every requisite order and question is received and answered by the most distant ships of a fleet.

To the adopting this, or a similar mode, in land service, the following are objections: that in the latter case, the variety of matter necessary to be conveyed is so exceedingly great, that the combinations would become too complicated. And if the person for whom the information is intended should be in the direction of the wind, the flag would then present a straight line only, and at a little distance be invisible. The Romans were so well aware of this inconvenience of flags, that many of their standards were solid; and the name manipulus denotes the rudest of their modes, which was a truss of hay fixed on a pole.

The principle of water always keeping its own level has been suggested, as à possible mode of conveying intelligence, by an ingenious gentleman, and put in practice on a small scale, with a very pleasing effect. As for example, suppose a leaden pipe to reach between too distant places, and to have a perpendicular tube connected to each extremity. Then,

if the pipe be constantly filled with water to a certain height, it will always rise to its level on the opposite end; and if but one inch of water be added at one extremity, it will almost instantly produce a similar elevation in the tube at the other end: so that by corresponding letters being adapted to the ver tical tubes, at different heights, intelligence may be quickly conveyed. But this method is liable to such objections, that it is not likely it can ever be adopted to facilitate the object of very distant communication.

Full as many, if not greater objections, will perhaps operate against every mode of electricity being used as the vehicle of information.-And the requisite magnitude of painted or illuminated letters, offers an insurmountable obstacle; besides in them one object would be lost, that of the language being figurative.

Another idea is perfectly numerical, which is to raise and depress a flag or curtain a certain number of times for each letter, according to a previously concerted system: as, suppose one elevation to mean A, two to mean B, and so on through the alphabet. But in this case, the least inaccuracy in giving or noting the number, changes the letters; and besides, the last letters of the alphabet would be a tedious operation.

Another method that has been proposed, is an ingenious combination of the magnetical experiment of Comus, and the telescopic micrometer. But as this is only an imperfect idea of Mr Garnet's very ingenious machine, described below, no farther notice need be taken of it here.

Mr Garnet's contrivance, is merely a bar or plank, turning on a centre like the arm of a windmill; which

being moved into any position, an observer or correspondent at a distance turns the tube of a telescope round its axis, into the same position, by bringing a fixed wire within it to coincide with, or become parallel to, the bar, which is a thing exextremely easy to do. The centre of motion of the bar has a small circle fixed on it, with letters and figures around the circumference, and a moveable index turning together with the bar, pointing to, any letter or mark the operator may wish to set the bar to, or to communicate to the observer. The eye end of the telescope has a like index and circle fixed on the outside of it with the corresponding letters or other marks. The consequence is obvious; the telescope being turned round its axis, till its wire cover, or become parallel to the bar, the index of the former necessarily points out the same letter or mark on its circle as that of the latter, and the communication of sentiment is immediate and perfect. The use of this machine is so easy, that we have seen it put into the hands of two common labouring men, who had never seen it before, when they have immediately held a quick and distant conversation together.

Fig. 1 pl. 20 represents the principal parts of this telescope: ABDE is the telegraph or bar, having on the centre of gravity C, about which it turns, a fixed pin, going through a hole or socket in the firm upright post G, and on the opposite side is fixed an index CI. Concentric to C, on the same post, is fixed a brass circle, of 6 or 8 inches diameter, divided into 48 equal parts, 24 of which represent the letters of the alphabet, and in the other 24, between the letters, are numbers. So that the index, by means of the arm A B, may be set or moved to