Cnoidal wave theory is appropriate to periodic waves progressing in water whose depth is less than about one-tenth the wavelength. The leading results of existing theories are modified and given in a more practical form, and the graphs necessary to their use by engineers are presented. As well as results for the wave celerity and shape, expressions and graphs for the water particle velocity and local acceleration fields are given. A few comparisons between theory and laboratory measurements are included.

In order to gain some insight into the phenomenon of gravity waves generated by underwater seismic disturbances, the tsunami, a laboratory study was made of the waves resulting from an idealized two‐dimensional model of the movement of a submerged body. Bodies of several shapes, sizes, and weights were allowed to drop vertically or to slide down inclines of several angles, in water of various depths, from several heights above the bottom, but always below the water surface. The surface time histories were recorded at a point close to the origin of the disturbance, and at a point or points some distance from the origin. In addition, motion pictures were taken of several of the tests. It was found that a crest always formed first, followed by a trough from one to three times the amplitude of the first crest (depending primarily upon the slope of the incline), followed by a crest with about the same amplitude as the trough. Because of the dispersive qualities of the waves, additional crests and troughs continued to form with increasing distance from the origin. The magnitude of the amplitudes depended primarily upon the submerged weight of the body, but also upon the depth of submergence, the water depth, and other characteristics of the generation. Within the limits of experimental conditions, it was found that the time intervals between the first and second crests remained constant regardless of the water depth, the distance of fall, the weight of the body or the time of the fall. It was, however, found to be related to the length of the body, with the period increasing with increasing length, and to the slope of the incline, with the smaller the incline the greater the period.

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Article discusses several problems and limitations involved in various aspects of offshore pipeline construction. Methods of laying offshore pipelines are described briefly, including the lay barge and push-pull methods. Some techniques and limitations are discussed for several operations involved in pipeline construction, including weight coating of the pipe and field joints, and the construction of laterals and tie-ins to existing lines which involves problems in locating and raising the lines, welding, and coating valves.

The wave heights and periods from wave recorders installed off Point Sur, California, and Heceta Head, Oregon, have been compared for the period from April 1947 to June 1948. These data, together with some obtained at Point Arguello, California, showed that the ratio of the maximum wave recorded each day to the average of the highest ten per cent for that day was 1.46 and the ratio of the average of the highest ten per cent to the average of the highest one‐third of the waves each day was 1.29 for any place along this section of the Pacific Coast. It was also found that the average period of the swells (that is, excluding the local storm “chop”) was 12 sec.