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INTRODUCTION
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skillful attempts to restore them to their original state. Apart from a few obvious gaps, however, and the rather abrupt ending, there is no real evidence that the treatise in its present form is not a separate, fairly complete work. Its brevity is apparently the basis of most of the suppositions that the text as we have it is a mere fragment; but if due consideration is given to the nature of the treatise and to the extent of ancient mineralogical knowledge as shown by other sources, it will be seen that it covers the field indicated by its title in an adequate manner, even though it may not be complete.
Without being a purely descriptive or a purely philosophical work, the treatise seems to be an attempt to classify mineral substances on the basis of Aristotelian principles, and a number of specific examples are used, mainly for purposes of illustration, without any intention of giving extended descriptions. It may be inferred that Theophrastus mentions only a small proportion of the mineral products known to him and his contemporaries; for Pliny, though he draws largely from Greek authors, some older than Theophrastus, mentions about ten times as many kinds of rocks or minerals. Those mentioned by Theophrastus appear to be introduced mainly to illustrate in a general way contrasting behavior and distinctive differences in stones and earths, and he may not have intended to catalogue the numerous varieties that were known at the time. This would explain why he describes relatively few mineral substances in any detail, and why he pays so little attention to certain common and highly useful ones about which a good deal must have been known even in his day.
From the historical standpoint the treatise is of special interest because it represents, so far as we know, the first attempt to study mineral substances in a systematic way. For this purpose, Theophrastus divides them into two main classes, stones and earths, discussion of the latter being confined to the second and smaller portion of the treatise. Though few in number, the concise accounts of ancient chemical processes included in this division are of no little importance for the history of chemical technology. At first glance, the structure of the treatise may seem to be loose or even disconnected, but on closer examination it will be readily apparent that this is not so. From the very beginning Theophras-
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9
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