premise: basalt is a kind of material sent2: granite is a kind of material sent3: the mantle of the earth is mainly made of silicate sent4: silicate is a kind of material sent5: waves travel at different speed in different medium sent6: different media are made of different materials sent7: an earthquake wave is a kind of wave sent8: the crust of the earth is made of basalt or granite.
hypothesis: a prism can refract white light and split the light into all colors of visible light