In recent years much attention has been directed toward the application of neutron and gamma ray techniques to soil moisture and density measurements. This application of radiological measurements of these characteristics of materials of highway construction, of course, is of great interest to the highway industry since the performance of the total pavement system is highly dependent upon the condition of the embankment, subgrade, and base components of this system. An important measure of the state of condition of unconsolidated earth materials is their unit weights and moisture contents. The highway engineer undoubtedly would welcome any method or technique which would provide more rapidly and easily this essential information that may be used in the control of the construction of the embankment, subgrade, and base. The application of the neutron and gamma ray techniques to this purpose appears to offer some promise for the engineer and thus is worthy of his consideration
