This section is from the book "Cyclopedia Of Architecture, Carpentry, And Building", by James C. et al. Also available from Amazon: Cyclopedia Of Architecture, Carpentry And Building.
Sand and gravel are often found together. Gravel alone, when of sufficient thickness, makes one of the firmest and best foundations. Dry sand or wet sand, when prevented from spreading laterally, forms one of the best beds for foundations; but it must be well protected from running water, as it is easily moved by scouring. Clean, dry sand will safely support a load of 3,000 to 8,000 pounds per square foot; and when compact and well cemented, from 8,000 to 10,000 pounds per square foot. Ordinary gravel well tedded will safely bear a load of 6,000 to 8,000 pounds per square foot; and when well cemented, from 12,000 to 16,000 pounds per square foot.