A comprehensive study of previous investigations along the same or related lines should prove very helpful in outlining the work and preparing the report.

(For sample working plan see Appendix.) FORMS OF MATERIAL TESTED In general, four forms of material are tested, namely: (1) large timbers, such as bridge stringers, car sills, large beams, and other pieces five feet or more in length, of actual sizes and grades in common use; (2) built-up structural forms and fastenings, such as built-up beams, trusses, and various kind of joints; (3) small clear pieces, such as are used in compression, shear, cleavage, and small cross-breaking tests; (4) manufactured articles, such as axles, spokes, shafts, wagon-tongues, cross-arms, insulator pins, barrels, and packing boxes.
As the moisture content is of fundamental importance (see WATER CONTENT, above.), all standard tests are usually made in the green condition.

Another series is also usually run in an air-dry condition of about 12 per cent moisture.

In all cases the moisture is very carefully determined and stated with the results in the tables.
SIZE OF TEST SPECIMENS The size of the test specimen must be governed largely by the purpose for which the test is made.

If the effect of a single factor, such as moisture, is the object of experiment, it is necessary to use small pieces of wood in order to eliminate so far as possible all disturbing factors.