Plutonism was another school of geology popular from the end of the eighteenth century to the beginning of the nineteenth century that opposed the theory of neptunism. A proponent of plutonism was the Scottish geologist James Hutton (1726–1797). The theory stated that granite was the result of the melting of the interior of the earth. At the edges of large granite bodies, granite dykes penetrated into limestone layers, and the contact between the dykes and the limestone produced a burning phenomenon that demonstrated the effect of the high temperature due to lava intrusion. Careful field observations showed that most of the minerals contained in basalt had gone through several stages of melting, gradual cooling and crystallization. Plutonism challenged and superseded the erroneous Neptunism theory.