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of keeping the balloon at a certain elevation. After expending ballast to make the balloon rise to a certain elevation for the sake of reaching a particular current, some change of temperature produced by the sun or clouds will often affect the delicately balanced machine and alter its altitude. If it has risen higher, gas must be sacrificed to attain the lower level; if it has descended, more ballast must be expended. In this way gas and ballast are quickly exhausted. It is such facts as these which make the successful experiment carried out by M. L'Hoste last August so worthy of note. In his voyage across the Channel he made use of a piece of apparatus called "A Flotteur Frein." This acted as a kind of floating anchor, or brake; and was a cylindrical iron vessel with a conical air chamber at the top, 1 mètre 60 centimètres in length, 22 centimètres in width, weighing 10 kilogrammes when empty, and 60 kilogrammes when filled with salt water. The flotteur was attached to a bar underneath the balloon, on which a small sail was hoisted. The important function of this flotteur is, that by its means the same altitude of the balloon can be maintained when the favourable current is once found. By means of this flotteur the water itself can be drawn up into a reservoir in the balloon and utilized as ballast after sunrise, when the expansion by heat of the sun's rays would otherwise have caused it to shoot upward. By this method of adjusting the altitude of the balloon, several important observations, of the various currents of air about which we know so little, might be taken; and it would be well if Governments organized experiments with these various currents, as well as with elaborate screws, worked with power that is inadequate for the purpose of propelling a balloon against a powerful wind. Perhaps the aerial machine of the future may be directed by utilizing in a thoroughly scientific manner these varying currents. In such a system of aërial locomotion, perhaps the screw may be used as a kind of makeshift in a dead calm, when a change of level is not desirable, like the oars, when there is no wind to fill the sails.

Air-routes, in the future, may be perhaps as valuable in their way as are the trade-winds in theirs. To these winds, as much as to any other factor, commerce owes much of its development. But the air-routes will not so well lend themselves to merchant princes, rather to Governments and ministerial offices. Fancy the size and cost of a balloon capable of carrying a shipload of elephants' tusks! I am also afraid that to those who consider comfort of more value than time, balloon locomotion will not commend itself; for I can assure them that some “mal d'air” is even worse than "mal de mer." But for messengers, for Cabinet Ministers when speedily summoned, and for aides-de

camp on service, to be blown from London to Edinburgh on one side of the clouds, and to return a few feet higher on the other, all in the space of a few hours, will be an advantage recognizable, anyhow by the nation, if not by the travellers.

One of the most practical uses of balloons in war is for signalling. The utility of balloon signalling consists in the elevation obtainable. Any accepted method of signalling may be used in the car of an ordinary captive balloon-e.g., flag signalling or lantern signalling. But signalling from the car of a balloon necessitates the use of a balloon of considerable size, to secure the required lifting power. This limits the practicability of such a method. About a year and a half ago it occurred to me to so apply electricity to a captive balloon, that a method of flashing signals from a balloon is practical while the operator remains on the ground. Thus the weight of the operator is obviated, and consequently the balloon can be of such a size as to be extremely portable.

In the interior of a balloon, which is made of a material that is perfectly translucent and filled with hydrogen or coal gas, are placed several incandescent electric lamps. The lamps are in metallic circuit, with a source of electricity on the ground. In the circuit on the ground is an apparatus for making and breaking contact rapidly. By varying the duration of the flashes of light in the balloon, it is possible to signal according to the Morse or any other code. A convenient size for such a signalling balloon is a capacity of some 4000 cubic feet, or, if desirable, it can be made smaller than this. Varnished cambric is a suitable material. There are two separate arrangements for suspending the lamps inside the balloon: the one consists of a holder made like a ladder, the lamps being placed one above the other in multiple arc. This arrangement is convenient, because of the small breadth of the ladder, which is easily admitted into the neck of the balloon. The ladder arrangement, however, casts a small shadow on the surface of the balloon. This is of hardly any consequence, but the existence of any shadow is obviated by using a holder in the form of a ball, from which project lamps at various angles. The form of contact-breaker which produces the intermittent flashes of light is in form somewhat like a Morse key. In reality it is essentially different. An ordinary Morse key, such as is used in telegraphy, would not withstand the large currents used to light the lamps. The contacts would be rapidly destroyed. In one form of contact-breaker there are carbon contacts. These can be easily renewed at trifling cost. In another form of contact-breaker there are rubbing contacts faced with platinum.

The leads which convey the electric current to light the lamps

must be as light as possible, consistent with the current they have to carry. It has been suggested by military authorities that such balloons would be useful for other purposes than for flashing signals-viz., as a preconcerted signal, or as a point light to guide advances or retreats.

The source of electrical power for working the lamps inside the balloon may be varied according to circumstances. It may be, (1) a small dynamo; (2) a storage battery; (3) a primary battery. Each of these three forms of electric power can be supplied in portable and convenient forms. In some cases, where there is a stationary dynamo machine in close proximity, storage cells may be conveniently used, as they can be charged from this stationary dynamo and brought into the field when required. A portable way of obtaining power would be to use a small gas engine with dynamo combined. This might be fixed on the waggon with all the other apparatus connected with the balloon; the engine would be worked by the gas, which is always a necessary adjunct to balloons. The gas supply might be a portable apparatus for generating gas, or else the method of storing gas in steel bottles could be adopted. This latter method has been carried out successfully by the Royal Engineers.

The advantages which I claim for this method of signalling are, briefly: It facilitates night signalling; it enables signalling to be carried on at great distances and in places where the ordinary methods would fail to be of use, such places as hilly and wooded districts; the apparatus is portable and simple. The invention has a short history. Shortly after its invention, some eighteen months ago, it was exhibited in model in the War Department of the Inventions Exhibition, 1885. While on exhibition there, the method was referred for Government trial under a committee of the Royal Engineers, at Chatham. During the time the model was being exhibited at South Kensington, some experiments were tried with a balloon of 4000 cubic feet capacity in the grounds of the Albert Palace. In this balloon were placed six lamps worked to sixteen or twenty candle-power. During these experiments the value of the methods for long-distance signalling was tested, the flashes of light from the balloon being observed with the naked eye as far as Uxbridge, a distance of sixteen miles. This was effected by less than 100 candlepower. The same apparatus was tried by the Government authorities at Chatham, after which trial the War Office gave an order for some of this new signalling apparatus to be supplied to the Royal Engineers. The system was again tested at Aldershot under the Signalling Department, when Major Thrupp, the Inspector of Army Signalling, arranged a series of experiments. On the day fixed for this trial there was a snowstorm and a fog,

two very unfavourable conditions for experiments in signalling; but nevertheless the signals from the balloon were read and answered by the signallers stationed some few miles distant.

The experiments hitherto conducted have been in connection with the army, but such balloons might also be useful to the navy. Their greatest use for the navy would be for coast signalling-signalling round corners; and it is to be hoped that before long some experiment in coast signalling will be carried out. In conclusion, perhaps, one ought to mention some particular occasion in history when this balloon-signalling would have been useful. I do not think we need look far back to find an instance. A short while ago there was a brave General shut up in a besieged city, with a few followers. Near at hand there were friends ready to help, but ignorant of the immediate necessity of their help. If from Kartoum there had arisen such an electric signalling balloon as has been described above, its flashes of light in the sky would have told the tale of the events below-a tale that would have been eagerly listened to, and perhaps Gordon would have left Kartoum, a conqueror, with his life spared for the future service of his country, that he loved so well. ERIC STUART BRUCE.

COME

ART. IV.-CRITICS AND CLASS-LISTS.

OMPARISONS are odious," is an aphorism commonly accepted-always, however, as reflection will show us, with reference to other people's comparisons and never to our own. There are in reality few commoner signs of any sort of mental alertness than the love of comparison and classification for its own sake, the tendency to dwell on degrees of superiority and inferiority as such. We can trace its presence equally in the schoolboy's deep curiosity or still deeper conviction as to "the best" and "the next best" in the various departments of cricket; in the Swiss tourist's unfailing interest in realizing which peak is higher and which lower than another; and in the national enthusiasm with which we regard a Newton or a Nelson. The affection is not easy to analyze; but its main ingredient is, perhaps, just the primary instinct to take a side-the instinct of partisanship which comes out among the spectators of every sort of contest, and which, e.g., would make ninety-nine Londoners out of a hundred, even though innocent of the remotest connection with

either of the contending universities, feel ashamed of admitting complete indifference as to the result of the annual boat-race. And in its more refined forms, where the element of hero-worship more or less enters, the instinct of comparison is really so valuable a way of adding interest to our intellectual life, that to be destitute of it may be accounted a misfortune and a proof of torpor. It quickens passive perception into active participation. A personal and emotional colouring is given to the act of judgment when one's own mind is recognized, not as a mere register, nor even as a passionless umpire, but as the sensitive and sympathetic stage on which one's heroes have actually to measure their strength and find their level, as the living and independent means through which the degrees of their excellence become distinct realities.

But like everything else which tends to a sense of one's own centrality, this habit of classification needs watching. In matters of daily intercourse we all recognize the odiousness of comparisons, when something that is moving our approbation is forced into disadvantageous contrast with something else, absent or unknown to us, the suggestion of which chills our pleasure in proportion as it warms the self-importance of the person who introduces it. And further on we may have to notice that this sort of bad manners is not wholly lacking in literary criticism. But I want now more particularly to notice another danger, one affecting not the manner but the validity of the criticism: I mean the assumption that because the justice of our classification is keenly felt, it is, therefore, demonstrable. We first attempt to give clearness and solidity to our position in our own minds by means of a formula; by entrenching our convictions behind some short and convenient canon or principle; neglecting thereby the chance that their truth, even for us, may be a very composite thing, whose strength and weight is really disposed over many points. And then, as the fact of having our own order of merit is inseparable from the impulse to convince others of its justice, and as the normal mode of convincing others of anything is by argument, we are naturally led into trying to make argument cover the ground, just as we tried to make our formula cover it; which, in turn, may involve us in the struggle to prove or confirm by argumentative methods what really belongs in large measure to the domain of instinct, and is as unamenable to reason as tastes and scents-much as though one should try to secure a sunbeam that has visited one's chamber by strengthening the floor and walls.

This danger belongs to verbal treatment of all imaginative work; but the field where it is most prominent is that of literary, and specially of poetical, criticism. In other arts, the need of a purely unreasoning faculty, of something in both producer and

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