SIO Reference 60-17. Skylighting which is symmetrical about the zenith generates a light vector diagram which is symmetrical about the vertical axis. When the sun departs from a position of symmetry the light vector diagrams become distorted. The extent of this distortion can to some extent be predicted from a knowledge of the scattering and reflecting properties of the water. The method of prediction is explained.

SIO Reference 60-24. In the application of radiometry to light measurements in the sea there are five important parameters which must be always kept in mind.1. The directional distribution of the light being measured.2. The bandwidth, or wavelength range included in the measurement.3. The state of polarization of the radiation.4. The magnitude of the radiant quantity measured, and5. The direction of propogation of the radiant quantity being measured.

SIO Reference 60-9. The report presents the detailed radiance distribution data obtained under overcast lighting conditions at the Navy Calibration Station on Lake Pend Oreille, Idaho, and also gives tables of radiance -K values for both the overcast and clear-sunny conditions.

Contract NObs-72039. Task 5. Report No. 5-4. For the solution of many problems having to do with underwater photography, vision, and television it is important to know the absorbing and scattering properties of the water. By this is meant the separate values of the absorption coefficient and the scattering coefficient.Instrumentation has already been devised to measure the total attenuation coefficient, which is the sum of the absorption and scattering coefficients and consequently it is only necessary to measure one of the two latter coefficients to evaluate all three.

U.S. Navy Bureau of Ships Report No. 3-2. This report describes the design features of an instrument for measuring directional luminance in the submarine environment.

SIO Reference 67-11. Biologists who are interested in the primary productivity of the ocean are often unable to make productivity determinations by the "in situ" technique because of the demands of other groups on the ship's time. Under these conditions it has been the practice to use a substitute technique called the "deck incubator" technique, in which the sample of plankton-bearing ocean water is transferred to a deck incubator and allowed to propagate for an appropriate length of time before determining the 14C uptake.From a radiometric point of view these two techniques differ to a considerable degree. In the "in situ" technique the plankton-bearing ocean water is returned to its original depth location where propagation takes place at normal radiant energy levels and with normal spectral and geometric distribution of the radiant energy. In the "deck incubator" technique the radiant energy level available is usually much too high and must be controlled, the spectral distribution and band width are abnormally different and the geometrical distribution of the radiant energy has no similarity whatsoever with the natural geometrical distribution underwater.Experimental results for any individual case are still further confused by the fact that the measured radiant energy must be sensed by a detector, usually of the photovoltaic type, having spectral and directional sensitivity properties unrelated in any way to those of the phytoplankton which are being studied, and magnitude response which is often arbitrarily nonlinear.These problems have been recognized to some extent by various workers engaged in primary productivity work and effective measures have generally been taken to control the magnitude of the radiant energy in deck incubator determinations. However, not enough has been done to control its spectral distribution, and very little, if anything, has been done to control the geometrical distribution of the radiant energy or to design a suitable photodetector or to design an appropriate deck incubator.Perhaps the most curious effort, in connection with the control of the spectral sensitivity of the photocell-filter combination, has been the deliberate selection of photodetectors which measure "lumens", and the general adoption of "lumens" as a radiometric unit for productivity work. The "Lumen" is, of course, a unit which was specifically orginated for radiant energy measurements relating only to human vision at the levels of photopic response. Its use in connection with photosynthesis is meaningless and is so recognized by many biologists who nevertheless continue to measure and publish in "lumen" units.From the point of view of international cooperation, the communication of results is exceedingly difficult. Not only do we have measurements of radiant energy which are meaningless for correlation with productivity, but every laboratory seems to have a somewhat different type of meaningless measurement.

SIO Reference 58-69. The object of this note is two-fold: (i) To define and discuss those recently developed concepts of geometrical radio-metry which are of greatest use in the experimental study of the light field in natural waters, (ii) To present a systematic development and discussion of the inherent and apparent optical properties of natural waters which are used in modem hydrological optics.

SIO Reference 59-39. A continuing program concerned with the visibility of submerged objects has been in progress within the Visibility Laboratory for morethan a decade. Early experimental and theoretical work provided a basis for predicting visibility by swimmers from instrumental measurements of water clarity. Further investigations, theoretical and experimental, and instrumental developments of many kinds verified and extended the original work and enabled this Laboratory to provide the U. S. Navy Hydrographic Office with an accurate water claritymeter and nomographic charts for the interpretation of its readingsin terms of the limiting range at which swimmers can sight any flat,horizontal object lying on the bottom of the sea.