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Three strand, hawser-laid, 25. thread yarn tarred. Multiply the square. of the circumference by the length in fathoms, and divide by 4.24 for the weight in pounds. Example: What is the weight 'of 100 fathoms of 6-inch rope? 36 100 4.24) 3600.000 (867.9 Ibs. 3312 2880 2544 3360 2968 3920 3816 Weight a Rope Will Lift When Rove as a Tackle--Multiply the weight the rope is capable of sus- pending. by the number of parts at the movable block, and subtract one- ' fourth of this for resistance... Exam- ple: What weight will a 6-inch rope lift rove as a two-fold purchase, i. e., four parts at the movable block? A 6-inch rope has a working strain of 6 tons, and this, multiplied by the four parts equals 24 tons, and % of 24 tons equals 6 and 24 minus 6 TAE Marine REVIEW equals 18 tons, that such a purchase will' sustain > peor tae To. Set a Patent Log.--Turn all pointers to zero; turn the hands or pointers forward, never backward. Finding a Ship's Speed.--Frequent- ly it is of some importance to know the exact speed of a ship at such times when the only opportunity to obtain it is from a 'short run. <The following method is available for any run, no matter how short: Rule.--Note the interval of time and the distance run. Then multiply the distance run' by the number of minutes in 1 hour and divide the product by. thé number of minutes in which the run was made. The result will be the speed per hour. Example: Ship has run 4% miles in 21 minutes, what is her speed per hour? Distance run 4% miles = 4.25 Minutes in 1 hour = x 60 21)255.00(12.14* a 45 42 30 24 90 84 *Speed per hour. ON OUR QUARTER-DECK | Where the Marine Review With Its Friends and Patrons Get Together and Talk It Over s It may not be out of place to mention the fact that "four quarter-deck" is very much un- like the quarter-deck of the olden time, where only the "Old Man" trod and ruled with the iron hand of dignity and discipline. Those were strenuous times compared with present day standards, but that they -were necessary then, is only too evident. On our quarter- deck you may say just what you think with- out running the risk of being knocked down with a belaying-pin or being keelhauled. department can be made very interesting with a little help from our readers. If you have anything of interest, or of interest to friends. send it in. Offer suggestions; tell what you like and what you dislike. It is our desire to please you. ° THE MYSTERIES OF FOG, To the Editor of the MARINE REVIEW: Since you have so kindly asked your readers to come aft to your quarter- deck with things of interest to them and others, I have taken the liberty of sending you a clipping from The Ocean, I am much interested in this question and I think other sailors will 'be. The magazine from which I took this article is several months old and I have as yet seen no explanation This some work on the mainmasthead. of the phenomena therein mentioned. What is your opinion? Yours truly, ; A SAILor, Following is the clipping spoken of. It needs no further introduction: A MYSTERY IN ECHOES, "A peculiar problem in marine. acous- tics is put before the readers of The Ocean for solution in this letter from a correspondent in Wellesley, Massa- chusetts: To the Editor of The Ocean: | In the autumn of 1893 I shipped as mate of a schooner bound around the Horn from Nova Scotia to Victoria, B. C. We had a good run to the Cape, making it in fifty-one days, with the usual Cape Horn weather, and nothing out of the ordinary happened until we were. well up the west coast. Here an incident occurred which I have never been: able to explain. Per- haps some of The Ocean's readers will be able to throw some light upon it. It was about four bells in the morning watch. The wind was very light, and a thick white mist enveloped the ocean, making it impossibie to see two ship's lengths ahead, but as the ship barely had steerageway and we seemed to be alone, nothing was thought of it, I had occasion to call out to'a man doing I noticed that af the captain, standing near me on the quarter- deck, listened pattentively for a minuté, then asked me to shout again and to listen also. I did so, and was astonished to hear the echo of my, Own yoice come back plainly: to me. . ' Knowing that we were two hundred miles from the nearest land, we looked: at each other for an explanation. Forward, I found the man on lookout peering out through the fog. He, too, had heard the echo. ; : The captain now hailed the masthead, and I heard the echo so plainly that. I sang out to put the helm down and let the ship come about, feeling sure that we must be close to something. As the schooner came slowly in stays, every creak of a block and the voices of the men were distinctly thrown back, as from a cliff. For about half an hour we lay by, watching developments. At the end of that time the fog lifted, and a few moments more saw a clear sky and ocean, with no land and not a sail in sight. Can any one explain what made the echo? I have talked to many men, but none offered any solution of the problem. ARTHUR TURNER. "On the water, sound often plays some queer tricks. It is on record, for example, that on one arctic expe- dition two men carried on a conver- sation' while separated by a mile and a quarter of smooth ice. But the fact that sound carries so easily over water or ice makes the incident de- scribed by Mr. Turner all the more extraordinary.' ; While navigators are quite familiar with the above phenomena, no theo-y has ever been advanced and accepted as a proper explanation. A very com- prehensive article was written on this subject and printed in these columns some six months ago. Sound is con- veyed in a very. capricious' way through the atmosphere; and apart from wind or visible obstructions, large areas of silence have been found in different directions and at different distances from the origin of a sound: These are called inaudible zones. 'They are shifting areas, however, so that what is an inaudible zone one moment may be an audible one the next moment. These inaudible zones are to be observed in clear. as well as in thick weather, even in. the clearest of weather and tinder a cloudless sky. Investigations -have proven that sound is liable to be intercepted by streams of air unequally heated and unequally saturated with moisture. Under such conditions the intercepted vibrations -are weakened by repeated reflections. Experiments have also clearly shown that rain, hail, snow and fog have no power to obstruct sound; in fact, it has been shown that the condition' of the air associated with fog is actually. favorable to the transmission of sound. While this may be true it is nevertheless a fact that sound waves. do not travel gs far or as fast during foggy weather as they do in- clear weather, due to the greater density . of the atmosphere. While' sound waves are interrupted in their travel owing to the changes in the air. cur- rents there is nothing on record to. show that the phenomena of echoes, -as above mentioned, have ever Qe-. curred in a clear atmosphere. v This