Volume 1

Petralogy. A treatise on rocks / By J. Pinkerton.

  • Pinkerton, John, 1758-1826.
Date:
1811
Catalogue details

Licence: Public Domain Mark

Credit: Petralogy. A treatise on rocks / By J. Pinkerton. Source: Wellcome Collection.

    17/670
    ©f language, styled Sub-species, with still smaller divisions of Varieties and Sub-varieties; so there remains a necessity for more minute discriminations in this new arrangement. In his excellent and elaborate system of chemistry Dr. Thomson seems to have hit upon the just and natural term, when he uses the word aspect as a chief characteristic. The parti¬ cular characters, says he, are the following: 1. Aspect of the surfacej 2. Aspect of the fracture; 3. A^ect of the distinct concretions ; 4. General aspect, &c.” As therefore the most important object in the study of minerals is to distinguish them by their external characters, and especially by those apparent to the eye, the aspect becomes of such radical importance that it may with the greatest propriety be admitted into the distinctive nomenclature. The verb ^ aspecto signifies to view with great attention or earnestness, and affords a hint to the student that these subdivisions called aspects require strict attention and discrimination. Thus, while the Mode chiefly expresses the difference of chemical composition, &c. and the Structure the grand characteristic, the Aspect refers to more minute features. The term variety is unobjectionable, as it is equally applicable to objects of ani¬ mated or inert matter; and diversity may be used to imply a still greater difference than the variety presents. A very faint shade of difference might, if necessary, be called a lineament. Having thus briefly explained the present system, the result of the reflections and meditations of many years (for it is w^ell known that simplicity in a plan, or a machine, as it is the most perfect quality, so it is the last which is dis¬ covered), it may not be unnecessary to illustrate its necessity and utility by some further observations. The embarrassments of the former systems cannot be more forcibly evinced than by the following discussion by Wer¬ ner, in his important work on the External Characters of Minerals. I shall here add some remarks upon the division or natu¬ ral order of bodies in general, as well for example, as expla- Yarieties, kc* Werner’s difficulties.