cables. And I am prepared to assert that the quantity of electricity evolved by the decomposition of as much moisture as would be contained in a single drop of water, would be greater than would be obtained by the decomposition of a large quantity of zinc, and I believe I am borne out in this by the researches of Dr. Faraday. The electricity thus obtained would suffice to transmit the whole of the telegraphic communication between England and the continent for a week. I would further make my plans more explicit, with your per. mission.

Instead of forcing the current by battery power from end to end of the line, with all its attendant evils of induction, leakage, and affinity to short circuit-to say nothing of the difficulty to contend with earthcurrents, I produce in my cable a static change, and the communication at the distant end is nothing more than the result of a disturbed equilibrium of the electric current existing in the line, and may be more fully explained by the following illustration :-Take a tube, bend it in the shape of a syphon, and fill it with peas; and if you push a pea in at one end you push one out at the other, moving actually but one pea, but putting all in motion.

I am, &c.,

To the Editor of the Nautical Magazine.

WILLIAM P. PIGGOTT.

CYCLONES AND SAXBY'S WEATHER SYSTEM.

Sir,-Having in your last September number entered upon the im portant subject of cyclones, and given to the world a few opinions, which if proved to be well founded must become of great value to shipping interests, allow me to resume so far as to bring the registration of subsequent weather to bear upon such opinions.

I have pointed out two causes of weather disturbance, which, while derived from the same origin, viz., the interruption caused by the moon's position in declination, are essentially different in their operation: the one being electric and rapid in the production of consequences; the other mechanical and requiring considerable interval of time before its effects are felt in the British Isles, or as I have named them, primary and secondary.

As regards the primary, my letters on "Lunar Eqninoctials" (as I have been calling them for want of a better name (have perhaps sufficiently informed your readers, although from the nature of the subject it will be as well to complete a two years' public testing (ending in January next) according to my promise.

The secondary, therefore, will now be further considered. In your magazine for July last, I explained that a (nescis quid) species of electric action, which we call gravity or attraction, is disturbed or causes disturbance on our earth's surface at periods connected with the moon's motion: that both the sun and moon have such power.

When, therefore, these influences act in combination, or nearly in the same direction as regards our earth, it is but reasonable to expect greater results, especially when another increase of disturbance may be looked for when the moon is at her perigee. We should say that when these three influences are confluent, the greatest effects would result.

Now in your last September number I explained that upon an average cyclones were from nine to twelve days in travelling from the place of their birth (viz., the region of equinoctial calms, and near the line of no magnetic variation, not very far S.E. of Barbados) to the British Isles. That cyclones do reach us from the southward and westward is an accepted fact. My object is to show the periods at which such cyclones may be looked for in the English Channel.

Now, if we take the months of September and the present October we shall find first that in September, the 4th was the time of new moon, the 5th the lunar equinox, and the 7th the time of perigee (the "confluence" already referred to). Taking the moon's declination to be in all cases the greatest agent, and the others as mere accessories, nine days from the 5th will give the 14th as the day of warning for the East coast of England. But as the new moon occurred on the day before, it is not unlikely that disturbances were accelerated thereby. Accordingly, a reference to the diagram of barometric registry, &c., will show that during the 13th the barometer fell from 30-29 inches to 29.90, and we had a "gale;" not very heavy, but the gale lasted four days, therefore its duration would lead us to suspect that it must have been a heavy one somewhere. Looking at the veering of the wind I shonld say that the centre of the cyclone was due North of us on Sunday the 15th at about noon, and the sudden change of wind at Unst (Shetland) from S.W. to N.E. on the 15th is remarkable, as favouring this notion. But if this were a cyclone, it must have come up Channel from the S.W., (becanse such is the bearing of the line of equal variation in that locality,) so that its effects would be felt to the southward and westward of Cape Clear many hours before it reached the coast of Kent. Accordingly we find that on the 12th a "terrific hurricane" tried its strength upon the giant sides of the Great Eastern, some 280 miles westward of Cape Clear.

We were afterwards visited by a second cyclone, which I will briefly state owed its birth to the lunar equinox of the 11th of September, and reached us nine days after, (viz., on the 20th,) as indicated by the barometer, and was at its height on the 23rd, when I measured the wind's velocity at nearly sixty miles an hour. Accounts from Whitehaven speak of this as "the most fearful gale or hurricane that can be remembered," and describe its sudden shifting from S.S.W. to N.W., evidencing its revolving character: and from data obtained on board this ship, the centre of the cyclone was certainly in that direction, at that time.

As regards the month of October I will show (without encroaching unnecessarily on your space) that the 2nd (at 8h. p.m.) was the period of lunar equinox, 4th, new moon, 5th, perigee (another confluence of

influences). Now on adding nine to the 2nd we should have looked for cyclonic disturbances on the 11th. Need I trouble your readers with details when I assure them that although I have witnessed a "Norwester" off the Cape, I never saw the wind raise up spray like clouds of white steam from the sea surface as it did at Sheerness on the 11th inst? It was a frightful tempest while it lasted, and the wind reached, I should say, sixty-five miles per hour at least; it was felt all through Kent, and was quite unlike an ordinary gale,-besides we have the witness of the barometer, which emphatically declared it a cyclone. But a noteworthy circumstance attended this, as I believe it does all cyclones, and one which I have never seen or heard noticed, I give it therefore for the purpose of calling attention to another (possibly) valuable "prognostic." I allude to the "premonitory atmospheric wave." On the 11th inst., (and I mention it to prove the strength of my convictions, (a general muster was held by the commander-in-chief on board the guard ship of the steam reserve. Having noticed the rather rapid fall of barometer since midnight of the 9th, as succeeding a gradual rise during that day, and which seemed to me like the premonitory wave of a cyclone, I from this and the state of the barometer confidently informed my brother officers in answer to their remarks on the weather that a cyclone was approaching. No other symptoms beyond barometric or the wave" I speak of could have forewarned in time to have averted danger, for on the same afternoon the scene I have mentioned confirmed by the presence of all the elements of the cyclone that it was upon us and with power. (The "wave" I mention is of the same origin as that which precedes a vessel's bows in her course throngh the water, for a revolving storm propelled through the air at the rate of some hundreds of miles a day must, from its momentum in traversing a fluid, raise [an atmospheric] wave and I call this therefore "premonitory.")

As regards the fulfilment of my predictions as to lunar equinoctials, I will only in referring to the past say that without one exception the periods I had marked have most fully justified my warnings. Details are at the service of any of your readers who need them. But as to the future (repeating the dates already given) we may suspect as periods of disturbance,

November 5th or 6th-11th-19th-26th

December 2nd -9th-16th-23rd-30th.

I also warned against the periods November 2nd to 6th, and December 1st to 3rd, as being periods of the "confluence of influences" spoken of above; but I would further remark that we ought to beware of the cyclonic periods in November and December, viz., 14th and 15th of November, and especially the 11th of December, for in December the perigee, lunar equinox, and time of new moon happen within a very few hours of each other, and these occur moreover when the sun and moon's declination nearly coincide in the same hemisphere.

THE

NAUTICAL MAGAZINE

AND

Naval Chronicle.

DECEMBER, 1861.

BOMBAY HARBOUR: ITS LIGHTS, DANGERS, and Defences.

Numerous plans for the improvement of the port of Bombay have of late been proposed, both for its efficient lighting and pilotage, as well as its defence; but, although acknowledged to be desirable, little or nothing has been done.

The port of Bombay is increasing in importance in a political as well as a commercial point of view, having all the essential requirements for a naval arsenal, as well as a great commercial port. It may be rendered easy of access at all times, either by night or day, in all seasons of the year; but to an enemy, if not inaccessible, it may be made at least very difficult. Besides being the key to our Indian empire on its western coast, it is also the great depôt for military stores, and on these accounts its improvement becomes desirable. We will first glance at the boundaries of the barbour, its lights and system of buoyage at present, with the improvements of which these are capable; and then glance at its defences, especially those of its entrance, and the protection they afford to our mercantile fleet.

The island of Kenery or Kundaree, about one hundred feet high, forms the southern boundary of the entrance of this harbour. It is a small rocky island 11 miles South of the lighthouse. Vessels bound to Bombay should endeavour to make this island, particularly in the S.W. monsoon.

Malabar Hill, remarkable for its low insignificant flagstaff, half way down its sloping side, and the lighthouse on the South point of Colaba island indicate the entrance of the harbour. The lighthouse is NO. 12.-VOL. XXX.

4 L

about 130 feet above the level of low water and shows a revolving light, visible from the deck of a ship about sixteen or eighteen miles, but the tower is not so easily discerned in daylight, being lost in the surrounding trees and buildings. The S.W. point of Colaba, on which the lighthouse stands, dries out at low water spring tides to a distance of a mile and three-quarters.

A floating light, midway between the S.W. extreme of Colaba and the foul ground off Thull, lies in the fairway of the entrance, in seven fathoms at low water spring tides, about two miles from each, with the following bearings and distances of the principal points from her:

This light-vessel first appeared at her station in 1842, showing a plain bright light, which may be seen from ten to twelve miles distant. She burns a blue light every hour of the night, and a torch every half hour. She carries a red ball at her mast-head, and hoists a red flag when a sail is in the offing. But, strongly as she is moored with her heavy ground-tackle, she too often breaks adrift-even in the last S.W. monsoon she did so twice; an evil more likely to happen in bad weather than at any other time, when her services as à guide to the harbour-the lighthouse on Colaba being too far away-are most wanted. The fairway channel is again marked by a large red spiral buoy about three-quarters of a mile N.E.b.N. of the outer lightship, that has also the habit of breaking adrift in bad weather. And N.E. N. four miles and a half from same light-vessel is an inner one, called the Sunken Rock Light.

The inner light-vessel is moored to southward of that rock. She also carries a red ball at her mast-head and a red flag by day. Her light is a fixed bright light from sunset to sunrise. She may be also called a fairway light, and about quarter of a mile to N.N.W. of her is a red buoy, showing the position of the Sunken Rock. Here, again, the same evil of breaking adrift occurs, for it happened to her in the last S.W. monsoon.

We next come to the Oyster Rock, on which stands a beacon in the shape of a white stone pillar, about twenty-four feet high; and the Dolphin Rock is marked by a light showing green to the southward and eastward and a bright light to the northward, while to the westward it is screened. The light-tower was erected about the end of the year 1856; but the light-keepers were thought less of than the light or the duty of keeping the lamps trimmed, for there was no room for them in the building,-a mistake which is now being rec

tified.

The several shoals are-the Middle Ground, which is distinguished by a chequered black and white buoy on its southern end and a black