THE Schiller disaster served to turn public attention to the question of Fog-signals and Alarms; and some interest was felt in the evidence taken before the BOARD or TRADE Court of Inquiry, apart from that naturally induced by the details of the loss of the ship. The scope of the inquiry, in fact, embraced some important matters connected with marine affairs which had a bearing on the question of how to prevent such disasters in the future, not only -at the Scilly Islands, but on all the coasts of the civilised world.

Two points were—telegraphing from certain exposed lighthouse stations, either from the lighthouse itself, or from an adjacent building; the second was fog- signalling:—the fog-signals to prevent ships rushing on the rocks when light- houses are invisible; the telegraph to call for assistance from the Life-boat and Steam-tug when, in spite of the fog " alarm," a wreck has taken place.

Now it so happens, that in times long past, and before steam and " syrens " were thought of, lighthouses were built, and naturally they were built on the sites most advantageous for warning the ma- riner of danger; and therefore, when we look round at the present day for the most suitable places to put in telegraphic communication with the required assist- ance, we almost invariably find ourselves at the lighthouse. It is not unnatural that the TRINITY HOUSE should view with some distrust attempts to fasten on their magnificent and perfect system of light- houses, telegraphs or anything else which in the remotest way might interfere with the usefulness and entire trustworthiness of the lights; and it is not, therefore, very surprising that, notwithstanding the time that has now elapsed since ocean tele- graphy has been in common use, no attempt to connect isolated lighthouse stations by telegraph with harbours or other inhabited places has been made. It seems to be the -weak point of our system of placing each, great branch of our mari- time affairs under its own special govern- ment, that each separate department has a tendency rather to promote the interests of its own particular branch, than to co- operate with other departments in the one great object for which all alike are main- tained by the nation, viz., to lessen the perils of navigation. It is not reassuring, for instance, to hear it said that it would be impossible to have telegraphs connect- ing lighthouses with the mainland, in such places as the Bishop and the Smalls, because it would distract the attention of the light-keepers if obliged to attend the telegraph. There would be twenty ways of getting over such difficulties as that.

Nor is it required that the men in the lighthouse should watch for telegrams from the land: all that is necessary is, that when the men in the lighthouses stand hour after hour looking down upon hundreds of men and women straggling for life, against time, they should have the means, by a mere touch of a tele- graphic apparatus, of raising an alarm at the other end of the wire, which would speedily place every reserve of steam and Life-boat at the service of the perishing people.

Mr. J. N. DOUGLAS, C.E., in his instructive evidence, has pointed out a graver diffi- culty in the probability of the violent action of the "waves at the base of such lighthouses destroying any cable. But it will probably occur to most people who read the statement of the same gentleman as to the building of some of the light- houses, that the genius and the heroic courage which, gave us those splendid mo- numents of engineering skill and daring, may yet find a way to connect them by telegraph with the mainland—if the effort is made.

On the great principle that prevention is better than care, a more important problem than sending aid to distressed vessels is how to prevent vessels being wrecked in such thick weather that the lighthouse becomes useless. We have it on the authority of Mr. CUNNINGHAMS, the Secretary to the Northern Lights Com- missioners, that two first-class lights on the Calf of Man, which are visible 22 miles in clear weather, give not the faintest indication of light to each other in some fogs, though they are only 580 feet apart.

Recollecting this, and that the first im- pulse of a steamer's captain on thick weather coming on is to dose a lighthouse, to identify it and his own position if possible, it is not surprising to find that lighthouses, the salvation of the mariner when they can be seen, exercise a fatal power of attraction in foggy weather; and too many vessels, pushing on to the last in the hope of seeing the warning light- house, perish at its base, with the light still unseen overhead. It was long ago decided that the only cure for this evil was to supplement certain lighthouses with fog-signals, or sound-signals. There were also other places besides lighthouses which demanded an equal care.

It is pretty clear that in times (as we may hope) now happily gone by, fog- signals did not receive the attention from.

" the authorities " which their importance demanded. Yet it is not too much to say, that in the present state of the art of navigation; with the intimate knowledge | possessed by most captains of the coasts j to which they trade; with the admirable j charts showing the depth of water all round the coasts of these islands, even.

the lighthouses themselves do not hold a higher position in the scale of preventive measures against maritime disasters than ! fog-signals.

Rapid steamships render the question more-important daily; and no doctrine is i more futile than that put forward some- times in Parliament, by certain portions of the press, and certain official person- | ages, to the effect that to avoid disaster less speed must be maintained; for every effort of the shipbuilder, the engineer, and the sailor is concentrated primarily on that one object. Speed means money: loss of ships and life does not necessarily mean loss of money; and however much wise laws, yet to be enacted, may some day modify these facts, in their broad features they must exist to the end, and all the disasters in the world, be they multiplied never so many times, will not alter those conditions one iota. On the contrary, if the average speed of the ocean steamship 1 is 10 knots to-day, it may safely be i reckoned on as 20 knots this day ten ; years; and when Governments, through I the various departments responsible for } these things, say, as they have been vir- tually saying for many years, " My good people, if you would only not go so fast there would be fewer accidents/' they are giving utterance to a, truism which is en- tirely beside the question. Ships must and will go fast and faster, and the only point of practical utility to consider is whether the State has done all it can and ought to do to lessen the dangers peculiar to the requirements of modern oceanic commerce.

Twelve years ago the Secretary of the Commissioners of Northern Lights stated that the primary difficulty was to get people to understand what a fog was or to arrive at a standard which would enable a man to say " This is a fog." We have, probably, got a little more precise since then, and the persons who send in their weather reports to the Meteoro- logical Department are tolerably in ac- cordance when they report on the self- same weather of the same parts of the coast, which was very far from being the case then. But as to the best means of causing an alarm to be heard in foggy weather, or the best' place to put those alarms, in order to keep ships out of danger, we seem to have made but slow progress, especially when we find from the Report of Professor TYNDALL that a small mortar, charged with lj Ib. of powder, yielded a louder report than the usual fog-signal of Dungeness, which, the Professor thinks, would be unable to warn a steamer in foggy weather until she came " dangerously close." We learn from the Schiller inquiry evidence that the latest TRINITY HOUSE experiments are now concluded, and that there are in course of construction " thir- teen fog-signals for floating lights, and six for land stations;" and it will not be •uninteresting to glance at the nature of the experiments above alluded to, and the deductions of the distinguished Professor who conducted them.

In the summer and autumn of 1873, and spring of 1874, Professor TYNDALL, acting under the authority of the TRINITY HOUSE, superintended a series of observa- tions made by sea and land, and hia pro- 'ceedings and opinions are embodied in a Report presented to Parliament.

It is significant that the great authority up to that time wrote in 1708, and that the inference to be deducted from Pro- fessor TYNDALL'S experiments completely refutes the opinions of most previous writers.

Professor TYNDALL'S experiments were made with various instruments worked by steam or compressed air, one set of which were placed at the base of the South Foreland Cliff at 40 feet above high- water mark, and the other on the top of that headland at 235 feet above the j high-water mark. It was soon elicited that the signals on the top of the cliff had the advantage. A curious fact to begin with, and not in accordance with either popular or authoritative—shall we say superstition—on the subject.

The experiments began with a steam- whistle, an air-whistle, and two trumpets, or horns, worked by compressed air. To these were added, after a few days, guns; and, at a later date, the steam syren, an instrument due originally to Dr. ROBINSON and CAIGNYARD DE LA TOUE, but since improved by various persons.

Taking the guns first. There were used for experimenting with, a 13-inch mortar, an 18-pounder gun, and a Si-inch howitzer. With the same charges of powder (3 Ib. to 6 Ib.) the result was decidedly in favour of the howitzer.

The whistles were speedily out of court, whether worked by air or steam; and the struggle, with varying fortunes, according to the state of the atmosphere, lay be- tween the horns and the howitzer till the syren came into the field. Then, under most circumstances, the syren was the victor; but not quite all. On the 17th October, when the sound-ranges reached their maximum, that is to say when the atmosphere was more acoustically pene- trable than on any other day throughout the operations, the gun had a decided advantage. On that day the howitzer and other guns were heard on board the experiment steamer at 16£ nautical miles, long after the syren had ceased to be audible. This was about 2 P.M., calm and hazy. After this the steamer stood back towards the signal-station, and at 13J miles, with paddles stopped, " both syren and horns were heard very feebly." Still steaming back, at 3.30, distance 7£ miles, syren was heard " very loud," horns " very full," and 39 seconds after the puff of the gun was seen, "a loud report was heard." It must be remembered that the howitzer used is, in comparison with the average modern gun, a mere toy. On the other hand, at the moderate distance of 7 miles, in the direct axis of the mouth of the syren, that instrument was heard above the sound of the paddles, while the gnu was entirely inaudible, not only then, but again when the distance was reduced to 54 miles.

Against the gun-sound is the muffling effect of the wind on it in comparison with the effect of the same on other instruments, also the shortness of the report, rendering it essential that the ear should be on the watch to receive the sound, and its greater liability to be quenched altogether by local noises and momentary puffs of wind. On the majority of occasions, especially in. rough weather, at moderate distances, the syren had a decided advantage; and once the gun was inaudible at 550 yards against a strong wind, at a time when the sound of the syren was reaching the observers " with great intensity." The direction of the wind with regard to the position of the gun. and the hearer affects the gun more than the other in- struments. On a fine day, force of the wind 3, the sound of the gun fired at a distance of 1 mile to leeward of a vessel was much fainter than when fired at 3 miles to windward of the same; and so on throughout. Other instruments are by no means so dependent on the direc- tion of the wind.

But of all the interesting and important results of Professor TYRALL'S experi- ments, none exceed those relating to the kind of atmosphere most conducive, or the contrary, to the transmission of sound. But it is pretty clear they are not in accordance with the theories and opinions of the great authorities on the subject who have written during the previous one handled and fifty years.

Dr. ROBINSON, for instance, in the British Association Report fox 1863, speaking of the effects of fog in deadening sound, says, that at each of the innumerable surfaces where the particles of air and globules of water touch, a portion of the vibration (of sound) is lost. Professor TYNDALL points to his own incontro- vertible experiments, and pertinently asks, If that were so, how it is that on the 1st July the signal-sounds reached 12| miles, a thick haze prevailing; while on the 20th May, in a calm and hazeless at- mosphere, the maximum reach of the sound was only 5 to 6 miles? And the result of his experiments certainly goes to show that so far from, fog being a deadener of sound, it is transmitted a greater distance in foggy weather than in clear. Not—as the DUKE OF ARGTLL (writing on the result of his own observa- tions) remarks—not that sound is assisted by the fog itself. But that fog is the visible result of an act of condensation, which has the effect of removing aqueous vapour which hitherto has been mixed with the air in such a manner as to render it flocculent; in other words, not favour- able to the transmission of sound.

A very clear result was attained by actual fog experiment on Feb. 7th, 1874.

On that day a " very dense fog prevailed, thicker at sea than on land. On shore objects were invisible at between 50 and 100 yards." The observers, before em- barking from Dover Pier, heard the sounds of the fog-signals on the South Foreland, 2J miles distant, and describe them as " astonishingly powerful." The syren particularly "filling all the air with a loud and full sound. At the same time there was not the slightest difficulty in at once indicating the exact direction from which the sound proceeded." The steamer steamed out in the line of the axis of the syren and trumpet. "Whilst so steaming, at the end of 55 minutes the sound of the whistle was lost. After I hour and 55 minutes' steaming, lost both syren and horn, while under way, but having stopped the vessel and dropped a buoy (for after-verification of distance) ai II miles, the syren and horn, equal!/ powerful, were heard "giving good and serviceable sounds." The bearing of the sound was then noted, which exactly coincided with the real'bearing from the buoy afterwards ascertained. At 10.18 A.M. the fog began to break, and then sounds were not again heard. Similar results were obtained from the observa signals were on the verge of inaudibility. I great number of independent columns of The condition of the atmosphere changed | air in a widely different state of heat or closed again to 2 miles, the guns pointed ! of different rarefication we have before directly towards her. The howitzer and I explained, and would be strongly non- tions of those who remained on Dover Pier throughout the forenoon, and the keepers of the South Sand Head Light- ship. As the fog rolled away the sound of the signals became fainter or inaudible.

Professor TYNDALL calls attention to a comparison between the result of this day's proceedings and those of October 14,1873.

That day is " logged " in the morning as "crisp and cloudless," wind light S.W., force 1; sea slightly agitated. At 12.30, at 12 miles, the gun alone was audible; at 10 miles, with engines stopped, all the very rapidly, and at 2 o'clock, at 7| miles, stopped and listened; at first heard no- thing, at last, " very faintly," the syren.

Again, at 3 o'clock, returned to the Varne Buoy at 7f miles, and, while seeing the flash of the gun, were unable to detect its sound, and at 4 P.M. the gun, from to lee- ward, was inaudible at 4 miles. We have, in the two days' reports, proof that fogs do not deaden sounds, and that the clearest days apparently are sometimes the thickest days acoustically, and that the homogeneousness of the air will alter in a few hours so as to deaden the sound one- half, without any visual alteration in the state of the atmosphere.

Another remarkable day 'was July 3, calm air, smooth sea. At 2 o'clock, at a dis- tance of nearly 4 miles, neither horns nor guns were audible. The steamer closed to 3 miles and stopped: still nothing was heard, though the smoke of the guns and the puffs of steam from the whistles seemed close at hand. The steamer mortar, with 3-lb. charges, yielded a "feeble thud," and the 18-pounder remained in- audible. But on July 1st, two days previously, the sea and the wind being in a much more unfavourable condition, the signals had been heard, both horns and guns, nearly 11 miles off, on the same bearing. Professor TYNDALL, during a process of able reasoning on the result of that day's experiments, points out how long ago HUMBOLDT accounted for the noise of the Falls of Niagara being three times louder by night than by day, by the fact that, the plain between him and the fall consisting of spaces of rock and grass intermingled, in daytime the tempera- ture of the rocks was raised by the sun's rays 30° above that of the grass; and then from over every heated rock there, of course, arose a column of air rarefied by the heat. Thus a state of atmosphere was set up non-homogeneous—not of the same density throughout, but divided into a rarefication. That condition is the most unfavourable to the transmission of sound.

At least so HUMBOLDT evidently thought, and so Professor TTNDALL argues.

But to the latter the question arose, What peculiar conditions, on that 3rd July, made the air specially non-homogeneous ? " Whilst pondering this question," he says, "I became conscious of the exceeding power of the sun beating against my back, and heating the objects near me. Beams of equal power were falling on the sea, and must have produced copious evaporation.

That the vapour generated should so rise and mingle with the air as to form an ab- solutely homogeneous mixture, I con- sidered in the highest degree improbable.

It would be sure, I thought, to streak and mottle the atmosphere with spaces in which the air would be in different degrees saturated, or it might be displaced by the vapour." This state of the atmosphere would, of course, be coincident with the air-columns homogeneous, fully accounting for its extraordinary acoustic obstructiveness.

Later in the same day, strongly con- clusive evidence was obtained. At 3.15 P.M., a cloud came across the sun, and completely shaded the space between the steamer and the fog-signal station on the South Foreland. The production of vapour was of course checked, and the different columns of air had time to mix, I and thus every minute the atmosphere be- I came more homogeneous, and (as TYNDALL ; expected), as a necessary consequence,; more favourable to the transmission of sound. The steamer was immediately pressed seaward at full speed to the " last [ point of inaudibility." This was at 3 miles from the station. The sounds had got [ there before them. They were distinctly j heard. Proceeding on. to 4 miles, the ! steamer was in advance of the sounds. A ' boat was moored there with two observers, I and the steamer pushed on to the light- ship. At 15 minutes after the steamer [ left, the observers in the boat hoisted their ! signal. The sounds of the fog-signals had ! just reached them. Thus the air becom- i ing momentarily more homogeneous, the sound momentarily travelled a greater dis- tance. For it must -be remembered that throughout the day the fog-signals never ceased to send forth their notes. At the ! Yarne Buoy, nearly 8 miles distant, a little later in the afternoon, the steamer heard all the signals clearly. Thus between 2 j P.M. and 6 P.M. the intensity of sound had increased 16 times, with, no visual altera- tion of the atmosphere, the wind and sea remaining the same.

We have, as the Professor points out, | in all this, and in similar deeply interest- ing experiments, explanations of many curious and unquestionable facts in his- tory. Thus, in the battle of Cassano, be- tween the Due DB VBNDOME and the PRINCE EUGENE, a corps under the Duke's brother, only 5 miles up the river, did not come to the assistance of the Duke as ex- pected, from hearing nothing whatever of the cannonade. At the battle of Monterean,! between NAPOLEON and the KING OF I WUBTEMBEBG, which lasted 7 hours, no | sound was heard by PRINCE SCHWARTZEN- BEBG'S army 13 miles up the river. Field- Marshal DAUN, stationed with his men 4J miles from the field, heard no sound of the battle in. which. FREDERICK THE GREAT overthrew LANDON, While Professor DOVE, of Berlin, who has collected these instances, says that he himself failed to catch any sound of the battle of Katzbach, from which he was distant 4i miles. Yet the same observer heard the cannonade of the battle of Bautzen, from which he was distant 80 miles; while Sir JOHN HERSCHELL, in his "Essay on Sound," tells us undeniable instances of such sounds being heard at 180 and 200 miles.

Sir JOHN HERSCHELL also refers to the instance of Lieutenant FOSTER, in PABBY'S arctic expedition, carrying on with ease a conversation across the frozen harbour oi Port Bowen, at a distance of 1J mile.

Sir JOHN HERSCHELL, attributed the fact in a great measure to the smooth surface of the ice. Professor TYNDALL says that nothing could be smoother than his sea on the 3rd July, and attributes the Port Bowen incident to the " absence of fioccu- lence." In other words, to the entire state of homogeneousness of the air, from there being no opposite agents immediately at work, such as extreme heat, acting coin- cidently and suddenly with the contrary influences.

The results of all the Professor's experi- ments go to prove (a) that fog is not a deadener of sound; (6) that remarkable changes take place in the acoustic con- dition of the air in a few hours of time, without any visible cause, to the ordinary observer; so that a seaman who hears a fog-signal over some well-known, danger at a distance of 7 miles, when leaving port, may, on his return a few hours later, find the sound inaudible a fourth part of the distance, though there may have been no apparent change in wind and weather, (c) That the sound of guns is deadened to windward, in proportion to the distance it is carried to leeward, in a greater degree than compressed air or steam fog-signals; and that the sound of a gun is greatly in- creased when pointed directly towards the hearer: also it has one great advantage in foggy weather, in that the glare of the light of its discharge is visible through the fog, when no sound may be heard from it or other fog-signals. Also it is very cheap, and can be placed anywhere, (cf) That the syren, however, is superior to tie gun and all other instruments, but it requires space—and money. Its limit of range in calm weather, under favourable conditions of atmosphere, is about 16 miles: in calm weather, under unfavour- able conditions, 2 miles. Of course violent gales still further reduce that limit; and so would local noises, such as the roar of wind through a ship's rigging, or seas breaking on rocks. It is note- worthy, however, that by far the greater number of dangerous fogs and fog-wrecks occur when it is not blowing hard.

We have thus a certain preliminary base to work on ; and it would seem now to be a mere question of whether the nation (or the authorities who represent the nation) consider that so many ships, so much treasure, and so many human lives which, are annually lost to the country from the absence of proper fog-signals on dangerous points of our coast, are worth so much money as the introduction of the said fog-signals generally will certainly entail on the national exchequer. As a mere matter of successful science, the world might be content to wait: it may be questioned whether it will continue to view with complacency for an indefinite time Schiller disasters and the like—cer- tainly preventable by means which science has long placed in our hands. In the meantime, the question is not without interest to poor Jack; and it is to be pre- sumed that many possible widows and orphans of sailors will pray that the change may be " in our time "! Professor TYNDALL gives a blow, at part- ing, at the existing system and systems, in the story about the Cape Eace syren.

The syren tried by him at the South Foreland was constructed by the maker of the Cape Eace syren, and specially sent to JEngJand for these experiments.

The two instruments are, in point of fact, pronounced by the constructor as identical. Professor TYNDALL found that the syren could not be depended on, in calm weather, much beyond 2 miles.

In the official notice to mariners the Cape Eace syren is stated to have a range of " 20 miles in calm weather; 30 miles with the wind; and in stormy weather, or against the wind, 7 tb 10 miles." The Professor, astounded at such results when compared with those obtained with the twin instrument on the South Foreland, has the question asked by our "authorities" of the Dominion authorities: Who ascertained the range of the Cape Eace instrument?—What observations were taken before that appa- rently mendacious statement was put forth on official authority ? And after proper inquiries, the melancholy answer comes back from Ottawa officials, " I cannot in- form you on what evidence the statement made in the notice about Cape Eace is made." ... "I am unable to answer your question as to whether the great range of the Cape Eace whistle is founded upon trustworthy evidence, or upon suppo- sition only." In short, there is neither evidence nor experiment to appeal to, and the official statement is put forward on the hearsays of unknown persons. Pro- fessor TTNDALL, in substance, observes that, allowing for the possibly greater homogeneousness of American atmosphere, it is possible that the Cape Eace syren has been heard occasionally on calm, days at 20 miles; but the notice to mariners should be based, not on the experience of " some one " on an exceptional day, but on positive observation, on the worst hear- ing days. In fact, to take the opposite course—that adopted by the persons re- sponsible for the Cape Eace advertisement —is to deliberately sacrifice, wholesale, both life and property for the mere pur- pose (as far as any purpose beyond care- lessness can be imagined) of increasing the sale of the instrument.

Verily, the " little cherub who sits up aloft" would seem to have a hard time of it, notwithstanding that science sheds its bright gleams over the world with daily increasing splendour!