yet they have taken Care, that their weaker Reasonings, and even their Errors, cannot be very prejudicial to Posterity. The Causes upon which they have agreed, they did not presently extend beyond their due Strength to all other Things, that seem to bear some resemblance to what they tried. Whatever they have resolved upon, they have not reported as unalterable Demonstrations, but as present Appearances; delivering down to future Ages, with the good Success of the Experiment, the Manner of their Progress, the Instruments, and the several Differences of the Matter, which they have applied; so that with their Mistake, they give them also the Means of finding it out. To this I shall add, that they have never affirmed any thing concerning the Cause, till the Trial was past: whereas, to do it before, is a most venomous thing in the making of Sciences; for whoever has fixed on his Cause before he has experimented, can hardly avoid fitting his Experiment, and his Observations, to his own Cause, which he had before imagin'd, rather than the Cause to the Truth of the Experiment itself. But, in a word, they have hitherto made little other Benefit of the Causes, to which they have consented, than that thereby they might have a firm footing, whereon new Operations may proceed. And for this Work, I mean a Continuation and Variation of the Inquiry, the tracing of a false Cause doth very often so much conduce, that, in the Progress, the right has been discover'd by it. It is not to be question'd, but many Inventions of great Moment have been brought forth by Authors, who began upon Suppositions, which afterwards they found to be untrue. And it frequently happens to Philosophers, as it did to Columbus; who first believ'd the Clouds, that hover'd about the Continent, to be
