1) It was found that initial "air-dry" moisture content of soil and the method and period of wetting affected the proportion, obtained by wet-seiving, of water-stable aggregates of Cruden Bay soils. Tha drier the soil the slower the wetting and the shorter the period of wetting the higher was the percentage of water-stable (but not of semistable) aggregates. 2) Soil pH affected significantly the water-stable and water-semistable aggregation and the porosity of the Tillycorthie soil (Site -I) between pH 5 and pH ?s the water-stable aggregation is decreased and the water-semistable aggregation and the porosity are increased with increasing pH, and vice versa. Planting with Italian Rye Grass did not affect aggregation within tha period of 7 weeks growth, but dacreased tha porosity due to the presence of fresh roots in the soil cores. Of the chemical additives used, only V.A.IK1.A. (a miature of calcium hydroxide and a copolymer of vinyl acetate and the partial methyl ester; of maleic acid) improved the poor structure of the soil, its optimum effect being around pH 6. P?E.0. ;(PolyethyleneOxide) increased the uiater-semistabla aggregation, but decreased tha water-stable aggregation and the porosity 4,7. the optimum effect being around pH S.Calcium, iron or aluminium sulphates had no significant effects, 3)/ 3) The amount of uiatar-stable aggregates affected considerably the compactibility of tha Tillycorthie soils, while the pH effect mas small between 4 and 8, and the effects of the P.E.O. solutions were negligible* It appears that compaction measurements with the Bruca type of apparatus could be very useful for structure studies relating to the behaviour of soils under field cultivation. 4) tha shear parameters of thB Tillycorthie soil were affected by:sail moisture content The P.E.O. solutions within the concentration ranga 10-10Q0 ppm did not shout a beneficial effect on the shear parameters of the soil,apparently because of very strong absorption of the polymer from solution onto tho soil colloid surfaces.