All testing laboratories at the Atoll were under the supervision of the Principal Engineer, Test-Inspection Section, who made the work assignments, The Senior Testing Engineer was in physical charge of the laboratories, designating what tests were to be conducted and what methods were to be employed, It was the duty of the Senior Testing Engineer to evaluate the results obtained by his assistants and to report his finding to the Principal Enginerr in charge of the Section, A daily log was kept of all work performed, copies of which were supplied to the Principal Engineer for file and distribution to the AEC Resident Engineer and Holmes & Narver Engineering Manager. The laboratory staff included, in addition to the Senior Testing Engineer, two Assistant Engineers, two Test Inspection Engineers, and two Laboratory Technicians, The laboratory on Parry performed compressive tests only, and ample tank space was provided there for storing cylinders and beams in a moist condition, The full-time services of a Test-Inspection Engineer were required to make the compressive tests which were necessary to supply needed information to Users and to the laboratory on Engebi, A few requests were made by representatives of Users for tests of characteristics of timber and of reinforcing and structural steel, These tests were made, and results were transmitted to the Users through proper channels, The laboratory on Engebi performed many different kinds of tests on construction materials, but the testing of cement, asphalts, and aggregates comprised the bulk of the testing work, A very close check was maintained by the laboratory on the condition of cement. When a new shipment arrived, representative samples were immediately taken, The samples were taken from the palietized bags and given fineness, soundness, loss on ignition, time of set, and mortar strength tests in accordance with ASTM C-150-49. Fineness was determined by the 200-mesh sieve; as specified by ASTM C-184-44, 15 per cent or more being retained was cause for rejection, A steam chest soundness test, ASTM C-189-49 was conducted. The loss on ignition test was conducted in accordance with ASTM C-114-47, with balances of 0,01; and time of set test, ASTM C-191-49, by a Vicat apparatus. Moryar strength tests were made according to ASTM C-109-49 with 2 inch cubes made with Ottawa sand aged from two to seven days in & moist condition before being tested to destruction, The laboratory personnel and the Batch Plant Inspector working together kept a very close check on the aggregates used in concrete, No less than five daily gradations were run, and indicated changes in proportioning were made at once, Determinations of moisture content of the aggregates were made at least three times daily, with additioal moisture tests at the discretion of the Batch Plant Inspector. Changes in the mix were predicated upon the results of the several tests performed by the Batch Plant Inspector. As part of the Batch Plant Inspector's daily routine, he took slump tests at such intervals as he 5-31