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Tae Marine REVIEW SHAPING THE COURSE. By Clarence E. Long. (Continued from last week.) As the lead descends, the water is forced up the tube in obedience to a well-known law. It is simply that the volume of any given mass of air, or other gas, decreases: in the same proportion as the pressure on it increases. The chemi- cal action of the salt, where it comes in contact with the salmon color, turns it to a milky white (chloride of silver). This point of junction of the two colors, when the glass tube is applied to a graduated boxwood scale, tells the depth to which the lead descended. The sinker is "armed" in the usual way so that a specimen of the bottom is obtained at each cast. "Nothing can be neater than this arrangement. Its ad- vantages are as follows: Let the speéd of the ship be anything up to 16-knots an hour, or even upwards, bottom can be obtained at a depth of 100 fathoms without slowing or deviating from the course. Instead of requiring all hands "to pass the line along" two men and an officer are sufficient to work it under all cir- cumstances. A cast can be taken in 100 fathoms, and: depth correctly ascertained in from four to seven minutes, according to the speed of the ship. This great labor-saving ie admits of soundings being taken more frequently, thereby resulting in greater safety to life and property. -- A regular "chain" of soundings,-with correct "time inter- vals," is not only possible by this apparatus, but easy; and this latter is the sole method which can be depended upon to give the place of the ship with any degree of certainty, since a single cast is not only useless in the majority of cases, but is apt to prove mischievous in the extreme. How to Use Compass, Log, and Lead in a Fog.--Take a piece of tracing-paper and rule a meridian on it, Take casts 'of the lead at regular intervals, noting the time at which each cast is taken, and the distance logged, or timed, be- tween each two. The compass shows the course (which is not necessarily the course over the ground from a certain position on account of current, leeway, etc.). Now rule a line on the tracing paper in the direction of your course. Measure off on it by the scale of miles of your chart the distances run between casts. Opposite each-cast note the time and the depth ascertained. It is a good thing also to add the character of the bottom. Now lay your tracing paper down on the chart, which can be seen through it, in the neighborhood of the position you believe yourself to be in when you made the first cast. Slip i ile. it about till you find an agreement y between the soundings marked on ° / the chart and the series marked on jf the tracing paper. If your chain of ae soundings agrees with those on the y / / chart right under your 'course, all VEE is right. If' not, move the tracing J paper about, keeping the meridian line due north and south, till you find the place on the chart where you can get that chain of soundings on the same course and at the same distances. Ph 70 Gn 12 4$ 930 am 'p24 9am This is the omly method by which a ship's position can be found with any certainty on soundings in thick weather. There is no excuse whatever for the man who runs his ves- sel ashore, if he has not tried this. It is a fact that there can only be one place on the chart where this set of soundings will agree with the distances between the soundings. The great superiority of this method, when the navigator has to fall back upon soundings to ascertain his ship's po- sition, cannot be too much dwelt upon. With the patent sounding machiné there is no difficulty in putting it in prac- tice. Other sounding machines depend upon the principle of the rotating fly. A small cylinder, protected by brass guards, is caused to rotate in its descent through the water by vanes or blades set obliquely to its axis; this communicates mo- tion, by an endless screw or worm, to a train of toothed gearing. On the machine reaching the bottom, an arm falls and locks the rotator, so that it cannot revolve the back way as it is pulled to the surface. An index points to figures on a graduated dial, which indicates the depth of water reached. These instruments are very good, but they nearly always possess what may be termed an index-error--that is to say, they either show too much or too little. A patent sounding machine in operation on any lake ves- sel would prove indispensable for her safety in thick weather. The apparatus could be employed in several different ways: Many vessels are continuously employed in one trade, and consequently going over the same courses. If in clear weather, when passing the land aboard and on the right courses for making turning points, it would seem a good practice to take a series of soundings for some miles before and after making the turn in the course; also the sounding at the turning point. By keeping a-record of this it could be referred to at any time it was necessary to do so. Should the vessel then be running the course in a fog, and the master desirous of verifying his position, or to ascertain if the vessel is making good the course, the sounding machine can be put in operation and its record of depths compared with those taken when the master was positive of the ship being on the right course. Even where this is not previously done, the chart will give the depths sufficiently accurate for the pur- pose of locating the vessel. Even a sounding taken at the turning point in the course will make a pretty good "fix" if the bottom is uneven. The sounding should have previously been taken to verify the one given on the chart. To "fix" the position of ship by means of the safety curve on the chart, nothing could be neater or handier than this sounding machine to take the depths. When it is blowing a gale and snowing and freezing at the same time, and it be- comes necessary to ask information from the bottom as to the ship's whereabouts, every seaman knows that the opera- tion involves much labor. and loss of time, and considerable peril. Carelessness in. equipping vessels with proper instru- ments for coasting in thick weather, and the failure conse- quent upon it, of keeping a correct account of the place the ship is in, is the prevailing fashion of which owners are sometimes forcibly reminded when making good the losses by stranding. : The patent sounder can be used at any time and is so simple in operation, that after seeing it once or twice one cannot help but see fully into its warking mode, and the pamphlet of directions which goes with each machine will render the instruction unnecessary. The sounding machine is quite expensive but its cost is very Geniicant in com- parison with the time and fuel to be saved, as well as the cost of hottom repairs. As a matter of course, soundings are of little or no use where the bottom is nearly a level plane devoid of leading features. But those and similar deficiencies have to be made up by artificial aids in appropriate places approaching by vessels close to, in the choice of which aids and places some-