[85]. Dr. Blair thinks that the ancients were led in many instances by the comparison of habit, to ascribe similar virtues to plants; there does not however appear to be a trace of what may be called System, in the writings of Theophrastus, Dioscorides, or Pliny. Cæsalpinus was the father of botanical system, and he was probably the first who suggested the idea that the virtues of plants were discoverable by their structure and alliance to each other. In his preface to his work, “De Plantis,” he says ‘Quæ enim generis societate junguntur, plerumque et similes possident facultates.’ This idea was pursued by Petiver, an apothecary in the city of London, a name well known in the annals of Botany; there is a paper by him on this subject, in the 21st volume of the Philosophical Transactions, entitled, “Some attempts to prove that herbs of the same make and class, for the generality, have the like Vertue, and Tendency to work the same Effects.” Dr. Murray has adopted an arrangement founded upon natural character in his celebrated work entitled, “Apparatus Medicaminum”.
[86]. Russell’s Nat. Hist. of Aleppo.
[87]. The student will find an interesting dissertation upon this subject in a late work, entitled “L’Histoire Naturelle des Medicamens.” Par J. J. Virey, 1820.
[88]. Lord Bacon attributes the operation of purgatives to three causes, viz. 1. to extreme bitterness, as in Aloes, 2. to loathsomeness and horrible taste, as in Agaric and black Hellebore, and 3. to a secret malignity, as in Antimony, &c.
[89]. This might be illustrated by the recital of numerous fallacies to which our most simple perceptions are exposed from the powers of association, but I will relate an anecdote, which to my mind elucidates the nature and extent of such fallacies more strikingly than any example which could be adduced. Shortly after Sir Humphry Davy had succeeded in decomposing the fixed alkalies, a portion of Potassium was placed in the hands of one of our most distinguished chemists, with a query as to its nature? the philosopher observing its aspect and splendour, did not hesitate in pronouncing it to be metallic, and uniting at once the idea of weight with that of metal, the evidence of his senses was even insufficient to dissever ideas so inseparably associated in his mind, and, balancing the specimen on his fingers, he exclaimed, “it is certainly metallic, and very ponderous?” Now this anecdote is not related in disparagement to the philosopher in question. Who could have been prepared to meet with a substance, so novel and anomalous as to overturn every preconceived notion?—A METAL SO LIGHT AS TO SWIM UPON WATER, AND SO INFLAMMABLE AS TO CATCH FIRE BY THE CONTACT OF ICE!
[90]. Virey, “Essai d’Histoire Naturelle et Physicolog: sur la perfectibilité de l’homme.”
[91]. Second Voyage of Captain Cook, vol. 4.
[92]. The cause of the green colour of oysters is sometimes an operation of nature, but it is more generally produced by art, by placing them in situations where there is a green deposit from the sea, which appears to consist of the vegetating germs of marine Confervæ and Fuci, and which impart their colour to the oysters. For this object the Dutch formerly took oysters from beds on our coasts, and deposited them on their own. Native oysters transported into the Colchester beds soon assume a green colour. It is unnecessary to refute the popular error which attributed this change of colour to the operation of copper.
[93]. We must admit that some of these allegories are too obvious to be mistaken. Homer attributes the plague that prevailed in the Grecian camp to the darts of Apollo; what was meant by this, but that it arose from the action of a burning sun, upon the marshes and slimy shores of Troas? and what, again, can be more obvious than the allegory by which Echo is made the daughter of air and earth?
[94]. Bacon’s works, vol. 5, p. 470. 4th Edit. London, 1778.