premise: as the amount of available water decreases , tree-growth rings will become narrower sent2: if something causes something else then the result of that something else indicate the properties of that something sent3: width is a property of size / shape and includes ordered values of narrow / wide sent4: dry environments result in narrow tree-growth rings sent5: a tree growing a tree-growth ring occurs once per year.
hypothesis: a narrow tree-growth ring indicates a dry year