In the Preface to his “Experimental Researches,” the great Faraday justly remarked that: “The date of a scientific paper containing any pretensions to discovery is frequently a matter of serious importance, and it is a great misfortune that there are many most valuable communications, essential to the history and progress of science, with respect to which this point cannot now be ascertained. This arises from the circumstance of the papers having no dates attached to them individually, and of the Journals in which they appear having such as are inaccurate, _i. e._ dates of a period earlier than that of publication.” Of the afore-named serials, the very important “Philosophical Transactions” have doubtless been most frequently alluded to herein, both in their original and abridged forms, and, for that reason, the assistance of representatives of the Royal Society has been sought in order to give a proper account to date, showing the difficulties which have throughout been encountered by its many successive editors. It will be seen, at pages 546–547, that there were numerous irregularities in the publication of the unabridged series from the initial date of 1665, only seven numbers having been issued from 1679 to 1682, whilst neither numbers nor volumes appeared between 1688 and 1690, and that, through lax editing, various numbers were often, during subsequent years, assigned to volumes differently designated. In the many abridged reports, irregularities are still greater, as shown at pages 547–548. During 1721, Motte edited “an abridgment, 1700–1720, in three volumes which was very incorrect” (“Dict. Nat. Biog.,” Vol. XXXIX. p. 194). The six volumes of 1720–1732 also appeared in two volumes, published 1733. The two volumes of 1719–1733 contained an “Index to the previous seven volumes” by different authors. This was made up by John Martyn, who published in five volumes an abridgment of the Transactions for 1719–1750, which he had previously issued in three sets of two volumes each. Mr. Samuel H. Scudder’s remarks as to various discrepancies are worthy of notice. He says (“Cat. of Scient. Serials,” 1879, p. 27) that “the Philosophical Transactions Abridged have been very irregularly issued. The first five volumes went through several editions (from five to two, according to the volume) between 1705 and 1781; the later volumes through only one, 1734–1756.” He adds: “There is a strange discrepancy here, the fourth edition of the first volume being sometimes dated 1731, sometimes 1781, and sometimes 1782, whilst the fifth edition of volumes one to three is dated 1749; the eighth volume is again sometimes dated 1734, sometimes 1747.” Were I to indite an _apologia_ for the present work, I could not hope to express it more happily than does Mr. J. J. Fahie in the preface to his “History of Wireless Telegraphy, 1838–1899”; or, I might adopt the words of two of the most learned French authors of the day: