them as much as possible of the full power of the magnetism. The top and bottom of the coil are attached to vertical stretched wires le, which serve to keep the coil stiff and form an axis round which it is free to oscillate, while they at the same

time serve to lead the electricity coming from the cable into and away from the coil. such a sensibly constant arrangement of weights

These wires are kept stretched by force as an adjustable spring or properly attached can give. The siphon is connected to the coil by a light fibre f, and this fibre.

is kept in a state of strain by the torsion upon the platinum wire t, from which the siphon depends. When the coil is deflected so as to increase the tension on the fibre, f, the top of the siphon is pulled nearer to the coil, and the writing extremity moves across the paper pp further from the coil; and when the coil is deflected so as to decrease the tension, the motions of the siphon are the reverse.

The two electro-magnets, which have each a pole m m shown upon the figure, are simply rods of soft iron wrapped round with copper wire, which is insulated by a covering of spun silk. So long as a current of electricity is sent through this wire the iron core about which it is wound becomes a magnet, but so soon as the current ceases to flow the magnetism vanishes almost entirely if the iron be very soft. The amount of deflection of the coil is proportional to the strength of the electro-magnetism, to the length of wire in the moveable coil, and to the strength of the current which flows through it; so that, cæteris paribus, the stronger the current upon the electro-magnets the greater the range of the siphon point across the paper. There is, however, a certain convenient range which can always be procured by regulating the battery power upon the electro-magnet and the current which comes from the cable. In the instrument itself every contingency in the working is provided for, and there are adjustments to regulate its every part, but the description of these would be uninteresting to many.

Suppose now that it is desired to transmit a message along the submarine cable from Falmouth to Lisbon. The source of the electricity to be employed is, we shall say, the ordinary Daniell battery, each element of which consists of zinc immersed in a solution of sulphate of zinc and a plate of copper immersed in a solution of sulphate of copper, the two solutions being kept separate by a porous separator. All the elements are joined up "in series," that is, taking them in order the zinc plate of each is connected to the copper plate of the next. If the last copper plate be joined outside the battery by any conducting circuit to the first zinc plate, a current will flow from it to the zinc. This conducting circuit may be a very complicated one, but still the current will find its way along it, always from the copper plate to the zinc, even although its route may take it round the world. In submarine telegraphy this conducting circuit is formed by the cable, the receiving apparatus, and the earth itself. If the zinc plate of a battery at any station, as Falmouth in England, is well connected to the earth-by one of the city water-pipes, for instance-or a large metal plate buried deeply in the ground, and an insulated wire be led from the copper plate to a distant station, such as Lisbon,

then so soon as the conducting circuit is rendered entire by putting the wire to "earth," there the current will flow from Falmouth along the wire to Lisbon, just as if the earth itself had led the current back to the zinc plate. On the other hand, if the copper plate be earthed and the zinc plate be connected by wire to Lisbon, where it is "earthed," just the reverse will take place, and the current will seem to flow from England to Lisbon through the earth, and will return to England by the wire. The sender at Falmouth connects the first zinc and last copper plate of his battery to a "signalling key," which is an arrangement for enabling him, by simply pressing down one or other of the two levers like piano keys, to control the battery so that he can apply the zinc plate or pole of the battery to "earth" and the copper pole to the cable, or vice versâ, for any length of time he chooses. The receiver at Lisbon sets the "mouse-mill" running, and by a battery, also joined up "in series," magnetises the electro-magnets of the recorder. connects the cable by means of the wire to the moveable coil, and the coil by the other wire to the earth; and so completes the conducting circuit between the zinc and copper poles of the sender's battery at Falmouth. Then, when the paper is running and the ink squirting so as to mark a straight line upon it, the instrument is ready to record the message from Falmouth. The sender there controls the electricity by means of the key according to a code of signals. The code universally adopted now is the Morse code, so called after the inventor. The fundamental basis of this code is two elementary signals, usually called the dot and dash. Every letter of the alphabet is made up of one or more of these signals. In the application of the Morse code to the recorder it is arranged that a dot and dash is transmitted when the sender presses the left and right-hand levers of the key respectively, just as in the case of the "needle instrument," and a dot is recorded by a motion of the siphon point towards the coil; and the paper being in motion, the ink traces out a small wave, while a dash is recorded by a wave on the opposite side of the axis of the paper.

The message being composed of a combination of such waves, with short intervals between each letter and longer intervals between each word, during which the siphon marks a straight line up the middle of the paper, presents a very serrated and, to the uninitiated, very unintelligible appearance, but an expert clerk can translate it as fast as ordinary handwriting.

There are of course various contractions for words conventionally employed, which facilitate communication in electric telegraphy, but without the aid of any of these, and by the use of an automatic sender-for few clerks can send

more than thirty-five-as many as 120 words a minute have been recorded through a land line by this instrument, each word averaging five letters and each letter three distinct signals. Owing to an inductive effect between the electricity in the interior conductor of a submarine cable and the sea water round its exterior, there is a retardation of the velocity of the electricity which is not experienced in land lines, and as a consequence the rate of transmission of signals through the latter is much greater than through the former, so that the number of words recorded from a cable will depend more upon the speed capabilities of the cable for transmitting signals than upon the receiving qualities of the recorder. Twelve words a minute is the working speed of the Brest and St. Pierre Atlantic Cable, whereas the longest land lines will transmit signals as fast as it is possible to send them. The retardation due to induction is made very apparent by the motion of the coil of the recorder. When the electric signals are sent through a land line into the coil it oscillates. quickly, and the waves traced by the siphon are sharp; but when the signals are sent through a cable the motion of the coil is slower and more prolonged, the waves traced upon the paper being flat curves.

When one stands alone by this beautiful instrument while it is at work, and observes the violet fire sparkling from the whirring "mouse-mill," the sure obedience of the coil to Nature's mysterious and inviolable laws, the apt inscription of the pen which,

With pulses electric,
Scatters its fine jet of ink,

and is guided by Nature's own fingers to the dictation of man many thousand miles away, he experiences one of those mental glimpses of admiration for human powers which he sometimes feels on viewing mighty enginery or triumphs of literature and art.

However much in after years telegraphy may extend its domain and connect the centres of human life throughout the world, it is scarcely too much to say that the electrical instruments of the future will be no important innovation upon those of our own time, unless indeed some hitherto unknown phenomena provide new laws to be the basis for invention no less fertile.

SPONTANEOUS MOVEMENTS IN PLANTS.

BY ALFRED W. BENNETT, M.A., B.Sc., F.L.S.

[PLATE LXXXIX.]

THA

HAT there are no "hard and fast lines" in Nature is a truth which is more and more forcing itself upon the minds of men of science. The older naturalists delighted to circumscribe their own special domains within sharply-marked boundaries, which no trespassers were allowed to pass. We have long given up the attempt thus accurately to map out the kingdom of Nature. Her varied productions are connected with one another by innumerable links and cross-links; and our systems of classification, even the most "natural," are but an imperfect human contrivance for bringing together those forms which present the most evident marks of resemblance or affinity. While the truth of this law is most familiar in the case of those smaller subdivisions of the animal and vegetable kingdoms-classes, orders, and genera-which are connected with one another by innumerable intermediate forms, it is none the less certain in the line of demarcation which separates these two great kingdoms themselves from one another. In attempting to draw up a definition which shall serve accurately and infallibly to distinguish between the Animal and Vegetable Kingdoms, we find ourselves compelled to abandon one supposed crucial test after another, and to content ourselves at last with framing, as in the case of the lower subdivisions, an assemblage of characters, by the tout ensemble of which we must decide whether our organism is an animal or a plant. So great is the uncertainty as to the actual boundary-line, that large groups of lowly organisms, such as those known as Diatoms and Desmideæ, have been regarded by experienced authorities as belonging to each kingdom; and one of the ablest of living naturalists, Ernst Haeckel of Jena, has proposed the division of the material universe not into three but into four kingdomsanimals, plants, protista, and minerals, the new kingdom of Protista including the most lowly organised forms of what are generally considered animals and plants, from the Flagellate