Navigational channel

“ The large ship under autopilot control will not anticipate the turn in a channel, and will not begin the turn until the antenna of the positioning system, presumably GPS and often located in the stern of the ship, is at the exact waypoint. ”

“ This channel was even more promising than the one which we had just emerged from, being almost double the width; but we were puzzled for the moment as to which direction to take, whether to head to the northward or the southward. The northerly-trending channel might lead anywhere; the southerly portion, on the other hand, looked as though it might possibly take us back to the ship, the spars of which were visible some nine miles away. ”

“ The navigable channel, with a beating wind between the ice and the land, was here from one to two, or two miles and a half in width; and this seemed, from the masthead, to continue as far as the eye could reach along shore to the westward.
We found the wind much more westerly after we rounded the point, which made our progress slow and tedious; the more so, as we had every minute to luff for one piece of ice and to bear up for another, by which much ground was unavoidably lost. ”

“ As we stand « 355 » on deck, we can see the black and open channel-way on every side of us, except off our port quarter: it is useless to talk of points of the compass; our floe rotates so constantly from right to left, as to make them useless in description. ”

“ Moreover, while the original channel first ran north, then north-east, for the twelve miles that were only to be covered by kedging—before it ultimately changed its course to south—in which direction the point of ultimate egress lay, the new channel left Mercury Basin at its western, or leeward, extremity, running first west, then south-west, and ultimately south, straight out to sea. Thus the whole distance could be traversed under sail and with a free wind. ”

“ Cut the speed of vessels is limited to six knots; through Gatun Lake they may make ten, twelve and fifteen knots, according to the width of the channel. A vessel may clear from the canal port at which it enters and, after passing through the last of the locks, put direct to sea without further stop.
The handling of a vessel all through the canal, except in the locks, is essentially the same as its handling through any charted channel where observance of signals, ranges and turns is necessary. ”

“ Thus the effect of currents and wave motion, and the maintenance of trim and equilibrium are not factors in the successful navigation of the vessel; in fact, navigation becomes surer on the surface, as one is travelling in a medium which does not constantly change like the surface water from the effects of winds, waves, and currents. When the divers desire to leave the vessel they go into the diver’s compartment, located in the forward portion of the ship, and close the door communicating with the living quarters. ”

“ But in three or four hours we reach our port of embarkation and go straight from train to boat, and are soon out in the Channel. Before we sail all the men put on lifebelts, in accordance with orders, much to the amusement of two or three blasé Canadian Officers returning to the Front, who, however, are soon unable to take any further interest in our proceedings, and seem from their earnest studies of the sea to be trying indelibly to impress upon their brains a distinct remembrance not of the ship but of the Channel itself. ”

“ Ships bound up Channel make for the nearest light, and from that shape their course until they meet with the next light. They feel their way, as it were, in the dark night by the handrail of these guides, and sometimes stumble on the very rocks that support the beacons themselves—the fog, as in the case of the Dunbar, allowing them to get within and under the danger flash. ”

“ Those who float swiftly along in well-appointed steamships through the almost straight channel 300 feet wide at the bottom, between towering hills, will find the sensation the more memorable if they will study somewhat the figures showing the proportions of the work, the full fruition of which they are enjoying. ”

“ No landmarks were discernible, or any visible thing to guide the navigator in this 'blind' part of the channel; yet, notwithstanding this, there was no lead, no sounding pole, or any means whatever used to ascertain the depth of the water, or to warn the navigator of his approach onto the 'flats' which lined that portion of the river. ”

“ The channel had barely depth enough in the middle to permit the passage of the Adieno; but as it was perfectly straight, and the water high in the lake, I considered myself competent to take her through. The boat minded her helm very prettily, and there was no current in the channel to interfere with my calculations, so that I did not regard the [250] place as very difficult navigation. I had been through the channel twenty times in the Splash. The pier ran out from the island to the deep water, so that I had only to run the bow up to it, and make fast to the ring. ”

“ From the tops of the hills on this extremity of the land you may see out into that they call the Chops of the Channel, which, as it is the greatest inlet of commerce, and the most frequented by merchant-ships of any place in the world, so one seldom looks out to seaward but something new presents—that is to say, of ships passing or repassing, either on the great or lesser Channel. ”

“ It was very quickly discovered that the vessel was next to useless on a shallow canal—the section of that particular waterway only averages from 40 feet to 50 feet in width at the surface, with flat sloping sides under water, tapering down to a mid-channel or gutter with an average depth of only 41⁄2 feet—inasmuch as with that depth (in mid-channel only) a screw propeller of sufficient diameter could not be used to utilise the power of the engines without a very great amount of “slip” and churning of the water instead of doing useful work. ”

“ It is not easy to describe the joy and lightheartedness we all felt as we passed the entrance of the Channel, bounding before a favourable breeze over the blue waves of the ocean, fairly embarked in the enterprise we had all so long desired to commence, and freed from the anxious and tedious operations of our protracted but requisite preparation. ”

“ A much smaller breadth might have been thought to suffice, and was at first intended; but it was found that the current in a narrow channel, the outer sea being many inches higher than the water of the gulf, would have been too rapid and violent for safety. The work had occupied fifteen Martial years, and had been opened only for some eight centuries. The water was not more than twenty feet in depth; but the channel was so perfectly scoured by the current that no obstacle had ever arisen and no expense had been incurred to keep it a clear. ”

“ Experience prefers for Channel seas a boat that can be driven through the water when necessity compels without any sense of danger, and that, if allowed to do so, will ride over the waves when no object is to be gained by making a short cut through. ”

“ Then, too, ships steer differently in shallow water than in deep. Sometimes a ship which, at sea, is responsive to the lightest shift of her rudder will behave like mad in a shallow channel. This is due to the shape of the hull and the paths followed by the displaced water as it flows past her sides and beneath her keel. In shallow water, the water that normally would flow beneath her cannot all do so, and the result is [Pg 204] likely to be a difference in the way she answers her helm. For other reasons a ship must not be driven too rapidly through a shallow channel. ”

“ There is one deep and safe channel—safe to those who are acquainted with it—through the centre of this open space, and which is sometimes used by vessels that wish to pass from one side to the other; but it is ever better for those whose business does not call them in that direction, to give the rocks a good berth, more especially in the night.
Mulford had gleaned many of the leading facts connected with the channels, and the navigation of those waters, from Spike and the older seamen of the brig, during the time they had been lying at the Tortugas. ”

“ Although it was an undoubted fact that we had actually found a channel leading from this basin to open water, the difficulties in the way of successfully carrying the ship through it were so great that we had very grave doubts of our ability to accomplish it. In the first place, the course of the channel was of so winding a character that, according to a very careful estimate, the ship would have to traverse no less than a hundred and ten miles of waterway before clearing the reef; consequently it would be impossible to accomplish the whole distance during the hours of daylight of a single day ”

“ In the first place, a clear channel is always found between it and the mainland, in which no sea of any formidable dimensions can ever rise, and now that modern surveys have accurately indicated where danger is to be found, this quiet channel is of the greatest use to the vessels frequenting that portion of the ocean, for they avoid the whole swell of the broad Pacific, which now thunders against and breaks harmlessly on the huge coral wall, instead of wasting its fury on the coast itself. ”

“ If the channel is very narrow, or there are many vessels at anchor, the safest way is to bring her head to the current, brace the yards full, and keep only sail enough to give her steerage, that you may sheer from side to side. If there is room enough, you will drift more rapidly by bringing her broadside to the current, keeping the topsails shaking, and counteract the force of the current upon the stern by having the spanker full and the helm a-lee. ”

“ I again ordered each captain to pick his own channel, and having a strong breeze and all oars working we managed to get above. In this place I discovered by experience that what we had found to be the best channel on that day, was the worst a few days after. The water falling six inches to a foot every day, continually changed the rapids, making a bad place better and a good place bad. Above this cataract we had thirteen miles of what we called smooth water with a current of from three to five miles an hour. ”

“ The narrowness of the channel causes the tides, both flood and ebb, to run with considerable strength, so that they cannot be stemmed without a fresh breeze. The rockiness of the bottom makes it also unsafe to anchor here: Put all danger may be avoided by keeping in the middle of the channel. Within the entrance, the course up the bay is first N. by W. 1/2 W. and N.N.W. something more than a league; this will bring the vessel the length of the great road ”

“ Such ranges are of course entirely free from compass errors, and should be noted whenever there is favorable opportunity. The value of the range in plotting will increase with the distance between the objects, and if the two are close in proportion to the distance to the vessel the direction will be weak owing to the uncertainty in drawing a direction through close points. Artificial ranges are often erected as aids to navigation, usually to indicate the course to be followed in passing through a channel. ”

“ As soon as the channel was three or four hundred yards wide, we warped into the clear water, and, making sail, rounded the point in safety, having no soundings with twenty fathoms, at one third of a mile from a small rocky islet lying off it. In the mean time the wind had been driving the ice so fast off the land as to form for us a clear communication with the open water before seen to the eastward ”

“ A ship's navigator knows to a small fraction of a mile the set of any ocean current, and from the known speed of his vessel he can keep "dead reckoning" with an accuracy that is nearly absolute. In fact, navigators have taken their craft across the Atlantic without once having seen the sun or stars, and yet, at the end of the journey, been within five miles of the desired destination. But in the air the currents either cannot be, or have not yet been, charted, and his allowance for the drift resulting from them must be obtained by direct observation on the surface of the ocean. ”

“ The popular belief in the existence of a channel, termed the Straits of Anian, connecting the waters of the Pacific with those of the Atlantic Ocean, in about the 58th or 60th parallel of latitude, through which Gaspar de Cortereal, a Portuguese navigator, was reported to have sailed in 1500, had caused many voyages to be made along the coast on either side of North America during the 16th and 17th centuries, and the exaggerated accounts of the favourable results of these voyages had promoted the progress of geographical discovery by stimulating fresh expeditions. ”

“ The hidden rocks may make a channel which looks good enough from the land, to be quite impracticable when you attempt it in the water.
Lastly, the current is seen to be swifter from the shore where you can observe its speed from a fixed point, than it seems when you are in the water where you notice only its velocity in relation to the stream on each side, which is itself all the time running at four or five miles an hour. But it is the positive speed of the current that ought really to be considered, for it is by this the boat will be urged against a breaker stationary in the river. ”

“ George’s Channel, which is not an amiable streak of water. It is subject to the same moods and tenses as the English Channel, and whoever crosses it must make sacrifices to Neptune in the form of discomfort if not other tribute. A company was formed some years ago to build docks here and to build steamers, but nothing has been heard from it of late, and the invention of the turbine engine and the construction of the fast steamers like the Lusitania make the voyage quite as short without the other drawbacks. ”