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A close look at hail reveals that stones differ in appearance. Some are white and others are more nearly clear. By breaking a hailstone in half, or by melting half of it away, one can observe concentric layers in varying degrees of whiteness or clarity, Close examination shows that these contrasts result from varying amounts of air bubbles in the ice. In ice containing air small bubbles look white for the same reason that snow looks white; the many ice-air surfaces at different angles form an efficient diffuser and reflector of light. The "Knights" proceed to show that during the "growth" stage, the stone has not yet solidified. That it is in fact "layering" new droplets on to the parent stone. I suggest that the term "embryo" best describes this stage. The stone is growing larger but as it is collecting more water, it is unable to solidify completely. The process can be considered to be similar to an egg shell of ice surrounding the inner. In order that it can solidify inwards, the collecting process must stop, as the process is liberating heat both externally and internally. In effect, the heat released in oreer tliat the wafer vapour can solidify spreads inwards as well as outwards. This effectively lifts the ~ _ _ __nO jDJernaLtemp.er.atu~e..of..tl'le-naiIstoFleoi*venting-jt-solidifyirrg;-1n-orctennartneTnneY , can solidify, the stone must enter an environment where the addition of water vapour stops, The insulating effect then has terminated and the stone will solidify. The process has similarities with the method of "Frost Protection" in fruit blossom. In this process, water is irrigated on to the flower at the time the temperature drops below freezing, At approx minus 2' degrees centigrade the irrigated water freezes over the flower surface, yet prevents freezing of the flower! This is caused by the "latent heat" given off by the water in the freezing process. As iong as more water is added, the process continues to see a build up of ice around the flower, but no damage is being caused to the flower. If the addition of water stops, the process changes to a pure and simple "freeze" and the flower is lost. In order to ensure no damage is caused, the addition of water continues until the air temperature rises and the process of adding water changes into a meltdown of the previOUSly frozen water. Our EMBRYO hailstone has a "fragile" stage in its growth. During this time it can be likened to a "honeycomb of egg shell like layers of ice, interspersed with unfrozen pockets of liquid and air cells". IT IS AT THIS TIME THAT THE HAILSTONE IS VULNERABLE TO "CAVITATION". "AL TITUDE" We found the subject of "What happens at what altitude" wantonly short on specifics and weak on practical conjecture. The general assumption that the hail stone is rotating in a continual circuit of "up and down" is far from the facts. No doubt it can do this, but common sense tells us that the differing wind speed within the cloud in a horizontal cross section will vary to the extent that there has to be vastly differing patterns to the joumey of individual stones. Add to this the "aerodynamics" of the individual stones and the relative density variance, we have a lot of stones doing their own thing within the cloud, Logic suggests that there is a degree of "running into each 4 Copyright 0 1994