VI. _Therefore_ celestial motions have no contraries--_therefore_ among celestial _things_ there are no contraries--_therefore_ the heavens are eternal, immutable, incorruptible, and so forth. It is evident that all this string of nonsense depends on the excessive vagueness of the notions of generation, corruption, contrariety, &c. on which the changes are rung.--_See_ GALILEO, _Systema Cosmicum_, Dial. i. p. 30. [31] Macquer justly observes, that the alchemists would have rendered essential service to chemistry had they only related their unsuccessful experiments as clearly as they have obscurely related those which they pretend to have been successful.--_Macquer’s Dictionary of Chemistry_, i. x. [32] Paracelsus performed most of these cures by mercury and opium, the use of which latter drug he had learned in Turkey. Of mercurial preparations the physicians of his time were ignorant, and of opium they were afraid, as being “cold in the fourth degree.” Tartar was likewise a great favourite of Paracelsus, who imposed on it that name, “because it contains the water, the salt, the oil, and the acid, which burn the patient as hell does:” in short, a kind of counterbalance to his opium. [33] See the Life of Galileo Galilei, by Mr. Drinkwater, with Illustrations of the Advancement of Experimental Philosophy. [34] The temporary star in Cassiopeia observed by Cornelius Gemma, in 1572, was so bright as to be seen at noon-day. That in Serpentarius, first seen by Kepler in 1604, exceeded in brilliancy all the other stars and planets. [35] Edinburgh Phil. Journ. 1819, vol. i. p. 8. [36] The abstract principle of repetition in matters of measurement (viz. juxta-position of units without error) is applicable to a great variety of cases in which quantities are required to be determined to minute nicety. In chemistry, in determining the standard atomic weights of bodies, it seems easily and completely applicable, by a process which will suggest itself at once to every chemist, and seems the only thing wanting to place the exactness of chemical determinations on a par with astronomical measurements.