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540 sone of the longest waves, A, could be obtained and recorded in the accom- panying blank (Fig. 2), noting also the speed of the vessel at time of observa- tion. From these a mean, or average, wave length could be taken for our purpose. Wave Period.—The wave period, or time in seconds between successive crests of the waves, could be taken by a third observer, on signals from the first and second. observers, stationed abreast the wave crests, and recorded in the data blank (Fig. 2), together THE for instead of sighting the wave hori- zontally, the observer will be inclined to sight the wave at an angle, or parallel to the inclined deck, which would show the wave to be of much greater height than actual. To get the true height of the wave, the observer should take a position on the ship at such height that he can sight the top of the largest wave, alongside, with the horizon line, or with the top of another wave close to the first one, when the vessel is practically on an even keel. The height from Observer Nas hr O/s7arrce-A—~| Observer Voz Sketch A sketch B-A/9/h+ Way Showing True Wave Height Vesse/ on Even Free/ Sketch C-wrong Way Showing Error jn Wave/leigh on Account of Ro// Th/s Arn (Gauge) Weighted in Lyrcess of rhe /tor/zorral Arn or SGT Sketch D Portabse Trim Gauge (Pine) FIG. 1—CORRECT METHOD OF FINDING SIZES OF WAVES with the speed of the vessel at time of observation. Second:—Height of Waves, Sketches B and C, Fig. 1. The height of a wave from trough to crest is usually obtained, on salt water, by sighting the crest, with the vessel in the trough, and at a moment when she is on an even keel. Owing to the nature of the cargoes carried in lake vessels, it might be impracticable to place the vessel ini the trough, but if, with the vessel head to wind, the height of the crest can be observed, it will be sufficient for our purpose. On the accompanying sketch C, Fig. 1, we have endeavored to illustrate how an error can be made in sighting the wave with the deck inclined, on a roll, water line, or from keel of vessel, to the observer’s eye will be the height of the wave, above the same_ point. The position of the observer should be marked, sc that height from this point to water line can be measured, in still water, and recorded in the blank B, Fig. 2, this being taken as the height of the wave. The observer might be hoisted in a bo’s’n’s chair, to proper height ,and distance from eye to deck measured. In order to take the observation when the vessel is on an even keel, a trim gage of some sort should be used, with a hand stationed at the gage to notify the observer when the vessel is on an even keel, for taking the observation of wave height (see sketch B, Fig, 1). The vessel’s ordinary trim’ gage MARINE REVIEW October, 1920 can be used or a portable gage might be constructed for the purpose. If ~ made with a horizontal arm attached to the gage arm or pendulum, this arm could be used as a sight or level (see sketch D, Fig. 1). The height of waves might also be observed as they: pass along the side of another vessel, close by. The storm waves on Lake Superior being longer and higher than on the other lakes, data on these are particu- larly requested, but data on the middle ' ground in Lake Huron, and on other lakes, are also desired and will be ap- preciated. This system is suggested as a means of obtaining the desired information, and though it may seem somewhat crude, we believe that the mean of a number of carefully taken observations will supply us with data of sufficient accuracy for our purpose. The com- mittee will appreciate any suggestions from masters as to other and_ better systems of procedure. In the making observations, care should be ‘taken by all of the crew not to endanger themselves, in any way, in order to get the information. It is requested that masters will supply, on the general data sheet, any particu- lar information regarding the free- board, stability and general seaworthi- ness of vessels, under various conditions of loading and ballasting, which may have come under their observation, and which they believe would be of value to the committee in carrying out its work. It is planned by the Great Lakes com- mittee, after the close of navigation this season and before working up the data sent in, to hold several confer- ences to discuss fully the subject of freeboard for lake vessels. A number _ of the masters will be invited to attend these meetings, along with the owners. We trust that we may have the co- operation of the masters and crews of vessels in procuring this information. While it may take some little time, patience and ingenuity, it is of such im- portance to the work of the freeboard committee, we feel confident that, in supplying us with the data, they will appreciate having contributed to so im- portant a work, and feel amply repaid for their efforts. Yours truly, Great Lakes Subcomniittee, H. C. SADLER, H. N. HerriMAn. A distinct improvement in the en- trance channel of the Columbia river is: noted in this year’s report of Col. J. H. Slatery. The government officials report a minimum depth of 40 feet and a width: of nearly 4500 feet. :