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April, 1919 This is not the contradiztion it seems, because most of the losses of the last few years have not been in the main channel, but in or at the entrance of inlets where the survey was inadequate; and where wrecks have occurred in the main channel— pinnacle rocks or sharp rocky ledges have been the cause. It is often im- possible to locate these by even the most careful hydrographic survey for ,the reason that a lead thrown at regular intervals from a moving ves- sel will not be likely to strike the top of the rock, and even if it should strike the top of such a pinnacle it would probably glance off and record the greater depth at the base of the rock, Locating the Rocks The only way to locate’ these pointed rocks exactly is by the use of the apparatus known as the wire drag. The main parts of a wiredrag are a horizontal wire maintained at any desired distance below the sur- face of the water by an arrangement of weights and adjustable upright cables extending to the surface buoys. This apparatus is towed by two launches, one at each end. As the drag passes through the water it will catch and show the location of any obstruction extending above the plane of the horizontal wire, which is usually placed at 60 feet, since most of the vessels plying Alaska waters draw not more than 24 feet. Knowing the loca- tion of the obstruction, the least depth on it can easily be found by sounding with lead and line from a small boat. It was in this way that practically all of the pinnacle rocks located by the coast and geodetic survey in Alaskan waters were discovered, and the value of a complete survey by this method of the rocky shores of south- eastern and southwestern Alaska is inestimable. The nature of the coast of the peninsula north of the Aleutian islands is sandy, so that such an exact survey is not needed in that region. A careful survey with large vessels is necessary, however; and the coast and geodetic survey has never a sufficient number of staunch, prop- erly equipped vessels for this purpose, so that the work has been only of a preliminary nature. The only vessels ever built especially for the work are the PArerson and the Surveyor, the latter completed in 1917. Survey work was at a standstill during the war. The main steamer route of the In- side passage from Dixon’s entrance to Skagway has been completely sur- veyed and 60 per cent of it has been swept with the wiredrag. The wrecks of recent years show where this has not been done. This work has been retarded by the lack of funds for THE MARINE REVIEW equipping and maintaining a sufficient number of units. Two parties have been engaged in dragging the Inside passage for the past three summers, but in order to complete the work within the next few years more. suit- able equipment and men trained for the purpose are needed. The greatest drawback has been the type of boats used. Having no boats built for the work, the coast and PINNACLE ROCKS ARE BEST LOCATED BY MEANS OF THE WIRE DRAG. 207 Staunch fishing boats with good engines are the best suited for wire- drag work of any that can be chart- ered, but here the government in renting then. must compete with the amount the owner can make in the fishing industry, where generous earn- ings may be relied upon. This makes the rental generally paid for them abnormally high. They are uncomfort- able for men to live in a whole sea- “A” IS THE DRAG SET AT DIFFERENT DEPTHS, “B”’ IS A’ PLAN-OF THE DRAG UNDER WAY, “C” SHOWS THE DRAG AGROUND ON A ROCK WHILE geodetic survey has been forced to rent launches and install the equip- ment at the beginning and dismantle it at the end of each season. been difficult to obtain the suitable boats for the following reasons: 1.—Pleasure launches usually have enough power, but their hulls are too weak. 2.—Fishing and working launches are generally of sturdy construction but are usually low powered. 3—Small gas tugs have too low freeboard and so much power that they cannot be regulated for towing the drag to obtain the desired result. sayy? Le Nas SHOWS HOW THE DRAG IS CLEARED son; for they have practically no living accommodations, and the smell of fish, which clings to them as long as they hold together, is nauseating. Vessels built especially for the purpose would be far more efficient and much less expensive to operate then those that have been used in the past. Have Designed Adequate Boats Officers of the coast and geodetic survey have made plans of the type of boats needed, and they are hoping that appropriations will be made for them soon. Their plans include two towing launches which should each