advice against the many casualties to which che mical experiments are liable. One general maxim is, always to endeavour from analogy to forefee the confequence, or probable refult, of the intended procefs, and when that cannot be done, to obferve the phenomena, and proceed with caution. ADVER ADVERTISEMENT TO THE SECOND EDITION. THE HE improvements in this second edition are very confiderable; as well in confequence of the rapid progrefs of the difcoveries made by Philofophers in all parts of the civilized world, as of the careful revifion the whole work has undergone. The additions are equivalent to a third volume, though by an alteration of the type, and page, this edition has been prevented from exceeding the former in bulk or price. Many additional figures have been inferted in the plates, and thofe numbered vii. and viii. are entirely new. Marginal references are likewife annexed, which it is hoped will be found eminently useful. In these the figures denote the pages, and the letters the paragraphs of the pages, where the proofs or Nov. Ift, 1786. CONTENTS. FROM the preffure of business, and repeated attacks of illness, the Author has found it im- poffible to finish the prefent edition without affiftance. In confequence, the whole of the section on chemistry has been rewritten by Mr. Accum, whose abilities as a chemist are well- known; and that on electricity has been re- vised, and the fection on galvanism added, by Mr. T. Churchill. All these, however, as well Three more planets having been added to our fyftem fince the aftronomical part was printed off, it becomes neceffary to fubjoin here all that is yet known of their elements. The planet Ceres, or Piazzi, was discovered by Mr. Piazzi of Palermo, on the ift of January 1801. Its mean distance from the fun is about 227 millions of geographical miles: the period of its revolution four years, feven months, and ten days: its mean longitude, Jan. 1, 1804, 10'. 10. 26° 44′: node, 2'. 21° 6' : equation of orbit, The planet Pallas, or Olbers, discovered by Dr. Olbers of Bremen, on the 28th of March 1802, is nearly the fame distance from the fun : the period of its revolution is 4 years, 7 months, II days: its mean longitude, Jan. 1, 1804, 9'. 29° 53′: annual motion, 2°. 18° 11': aphelium, 10.1°7′ node, 5'. 22° 28′: equation of orbit, 28° 25': eccentricity, o'.2463: inclination, 34° 39' greatest apparent diameter, 4′′.635. The planet Juno, discovered by Mr. Harding of Lilienthal, is about three times as diftant April 13, 1805. W. NICHOLSON, CONTENTS. |