"We can roughly divide the soil into three classes and call these sand, clay, and humus. The ideal soil has all three of these elements in it. Sandy soil is made up, as the name itself really tells, of broken up rock masses. One can tell this sort of soil by its lightness and the ease with which a mass of it drops apart. By the word lightness one does not mean colour or weight, but looseness. A clay soil may be told by its stickiness; its power to form lumps or masses; its tendency to crack and bake under the hot sun. Such a soil is called heavy. Humus soil is made up largely of decayed animal and vegetable matter. Its presence is told by a dark, rich colour. "In trying to improve the soil we are dealing with, we have first to think of its physical, and second, its chemical condition. "The great needs of the soil are air and water. Just think of all soils as made up of many particles; let us say like a lot of marbles, one placed upon another. Each given mass of particles has a given air space between every particle. Again, if a marble is dipped in water a film of water remains on it a short time. Let us think of the particles as always having a film of water on them. Then, as roots and root-hairs of plants strike down among these they find the two necessities, air and water. "Now sand is very loose and so lets the water drain down through it too rapidly. How shall we improve a sandy soil? Just add something to bind the loose sand particles together. Humus is good for this binding purpose. "Clay absorbs much water. Then its particles squeeze tightly together and so air is shut out. Add sand to clay soils, to lighten them. "Humus soil is very rich in nitrogen. This brings us to the chemical side of soils. There are many chemicals in soils which act as foods to plants, but only three are the essentials. If these cannot be unlocked from the soil, or are lacking, they must be supplied. These plant foods are nitrogen, potash, and phosphorus. "The chief source of nitrogen is manure; of potash, nitrate or sulphate of potash, and wood ashes; of phosphorus, bone ash or phosphates. How can you tell when one of these is lacking? Well, first it is well to know what each one does for a plant. Nitrogen makes fine, green, sturdy growth of leaf and stalk; phosphorus helps blossoming plants; while potash makes plump fruit. If foliage looks sickly then nitrogen is needed. If one wishes a good growth of leaves, as in lettuce, nitrogen is needed. If the fruit is small and poor, supply potash; while if the flower and stalk need better growth, add phosphorus. "Be careful in adding nitrogen. Nitrogen is the plant food which is most easily lost out of the soil. Study the soil you are dealing with, supply if possible what it lacks, and try to unlock to your seedlings the goodness already in the garden soil." The interesting talk ended. "Couldn't we meet oftener than just Saturdays?" questioned Jack.