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COMMENTARY
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accounts. Meander66 states that Thracian stone flames up when it is moistened with water and is quenched by oil. Dioscorides*7 increases the marvelous nature of the phenomenon by stating that the stone was ignited by water and quenched by oil. Pliny68 discusses the heat that is developed when water is added to Thracian stone, which he compares with lime, and also says that it could be quenched with oil. Evidently the story increased with the telling. Theophrastus was apparently the first to mention spontaneous combustion. Moreover, he seems to have been the only ancient writer to allude to this phenomenon in a reasonably clear and rational manner.
14. Liparean stone. This was evidently named from the volcanic group, called at present the Lipari Islands, lying off the northeastern coast of Sicily. These islands are still die scene of much volcanic activity. The locality and the description leave little doubt that this so-called Liparean stone was what we now call obsidian. Large quantities of this dark volcanic glass occur at certain places on these islands. The mention of pumice in connection with the Liparean stone supports the identification, for both these varieties of glassy rhyolite or liparite commonly occur together, often in the very way described by Theophrastus.
Stephanides,69 on the basis of a very literal interpretation of the statements in this section, identified this Liparean stone as a combustible mineral substance, possibly a volcanic rock impregnated with asphalt, but it is clear from what Theophrastus says in sections 19 and 20 about the creation of pumice by fire that combustion in the modern sense of the word is not to be understood here. The ancients apparently made little or no distinction between actual burning and the phenomena connected with molten material at a high temperature. Thus when pumice was formed by the expulsion of gases from molten volcanic glass at the time of solidification, this did not seem to differ from the combustion of a mineral substance such as lignite, especially since the
eeTheriaca, 45.
67 y, 146 (Wellmann ed., V, 129).
68 XXXIII, 94.
69 The Mineralogy of Theophrastus, pp. 211-12.
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