Punctuation errors were corrected. Inconsistent hyphenation was retained. “De la Lande” and “La Lande” both appear in text and were retained. “Shenier”, editor’s spelling of “Scheiner”, was retained. On p. 37, a paragraph break was inserted before "There is a clear example ...". On p. 44, “the” was changed from “The” (the usual method). On p. 85, “that” was changed from “That” (that a species). On p. 86, “that” was changed from “That” (that an instrument). On p. 118, “aëriform” was changed from “aeriform” (aëriform or igniform). On p. 178, “borrow” was changed from “brorrow” (to borrow a term from the grammarians). On p. 204, “sufficiently” was changed from “sufficietly” (but sufficiently dense). On p. 219, “quantity” was changed from “quanity” (quantity of gold). In footnote [5], “psychological” was changed from “pyschological” (most other psychological). In footnote [23], “that” was changed from “tha” (that we have nothing). In footnote [33], "72" was changed from “22” (Acad. Prior. ii. 72.). In footnote [60], “ix.” was changed from “x.” (Livy, lib. ix.). In footnote [71], “οὐσία” was changed from “οὐδία”. In footnote [86], “necessary” was changed from “necesary” (necessary to invent). In footnote [87], “liquor” was changed from “liqour” (the liquor rose). In footnote [161], “the” was changed from “th” (by the flame).]