The history of the eliding-rule, had it ever been properly given, would be matter for a few lines of our work, in the way of abbrevia tion and reference. As it is, we have not ouly to establish the main points, but also to point out a specimen of the manner in which the account of early English science has been written, Harris's' Lexicon Technic= ' (1716) informs us that sliding-rules 'are very ingeniously contrived and applied by Gunter, Partridge, Cogahall, Everard, Hunt, and others, who have written particular treatises about their use and application.' Stone's Mathematical Dictionary' (1743) has the same words. Dr. Hutton (' Math. Diet., 1815) informs us that they are variously (not ingeniously) contrived and applied by different authors, particularly Gunter, l'artridge, Hunt, Evcrard, and Coggleshall. Other writers repeat this sentence in their own ways, and the summing up is this :—the recognised history of the sliding-rule consists in the names of five persons; all our best English authorities are unanimous in stating that these men 'contrived end applied' sliding-rules, either ingeniously or variously ; but to the credit of this century be it spoken, that it was our historian who altered the chronological order, and spelt Coggleshall's name right : had it not been for the research of Dr. it might have been Cogehall to this day.
We now go on to something more like history, It is generally stated that Gunter invented the sliding-rule. This is not correct ; Gunter neither invented this rule nor wrote about it ; and though he was the first (On the Crosse-staffe, book i., cap. 6) who used a logarithmic scale, it was in the manner described at the beginning of this article, com passes being used to make the additions and subtractions. Gunter's rule is used up to the present time, under that name, in the navy, without any elides, The real Inventor of the slide was OrcfiTnIM (Moo. Div.), who was also the first writer upon it lie wu a man who set but little value upon instrumental aids, unless in the hands of those who had pre viously learned sound principles, which (as we have seen) ho himself testifies. In the year 1630 he showed it to his pupil William Forster, who obtained his consent to translate and publish his own description of the instrument, and rules for using it. This was done under the following title : ' The Circles of Proportion and the Horizontal Instru ment,' London, 1632 ; followed, in 1633, by an Addition, &e. ' with an appendix, having title, 'The Declaration of the two Rulers ior Cal culation.' The following extract from W. Forster's• dedication to Sir Kenelm Digby will explain the whole Being in the the time of the long vacation 1630, in the Country, at the house of the Reverend, and my most worthy friend, aud Teacher, Mr. William Oughtred (to whose instruction I owe both my iuitiation, and whole progress° in these Sciences), I upon occasion of speech told him of a Ruler of Numbers, Sines, and Taugents, which one had be spoken to be made (such as is usually called Mr. Gunter's Ruler), 6 feet
long, to be used with a payre of beams compasses. Ho answered that was a poore invention, and the performance very troublesome : But, said he seeing you are taken with such mechanical] wayes of Instru ments, I will show you what devises I have had by mee these many yeares. And first, hue brought to ince two Rulers of that sort, to bo used by applying one to the other, without any compasses: aud after that he shewed mee those lines cast into a circle or Ring, with another moveable circle upon it. I seeing the great expeditenesse of both those wayes, but especially of the latter, wherein it farce excelleth any other Instrument which bath bin knowne ; told him, I wondered that he could so many yeares conec.sle such uscfull inventions, not ouely from the world, but from my selfe, to whom in other parts and mys teries; of Art he had bin so liberal). He answered, That the true way of Art 'h is not by Instruments, but by Demonstration : and that it is a preposterous course of vulgar Teachers, to begin with Instruments, and not with the Sciences, and so instead of Artists, to make their Schollers only doers of tricks, and as it were Algiers : to the despite of Art, lease of precious time, aud betraying of willing and industrious wits unto ignorance, and idlenesse. That the use of Instruments is indeed excellent if a man be an Artist: but contemptible, being set and opposed to Art. And lastly, that he meant to commend to me the skill of Instruments, but first he would have me well instructed in the Sciences. He also shewed me many notes, and Rules for the use of those circles, and of his Horizoutall Instrument (which he had pro jected about 30 yeares before) the most part writteu in Latine. All which I obtained of him !cave to translate into English, aud snake pub lique, for the use and benefit of such as were studious, and lovers of these excellent Sciences." Oughtred gave his right in the invention (so soon as it was settled to be published) to Elias Allen, a well-known instrument-maker, near St. Clement's Church, in the Strand. In walking to and fro from his shop, he communicated his invention to one Richard Delamain, a mathematical teacher whom he used to assist in his studies. This Dolamain not only tried to appropriate the invention to himself, but wrote a pamphlet of no small scurrility against Oughtred, which the latter answered in an Apologeticall Epistle' fully as vituperative; which epistle was printed at the end of W. Forster's translation. It contains some quantity of biographical allusion, and must not be for gotten by a mathematical historian of the times. W. Forster's work was republished in 1660, by A. H. (Arthur Haughton, another pupil of Oughtred), with Oughtred's consent, but the dedication and epistle were omitted.