Nothing certainly can be more improving to a Searcher into Nature, than Objections judiciously made to his Opinions, taken up perhaps too hastily: For such Objections oblige him to re-study the Point, consider every Circumstance carefully, compare Facts, make Experiments, weigh Arguments, and be slow in drawing Conclusions. And hence a sure Advantage results; for he either confirms a Truth, before too lightly supported; or discovers an Error, and receives Instruction from the Objector. In this View I consider the Objections and Remarks you sent me, and thank you for them sincerely. When he found that he was in error, it cost him no struggle to recant. For a while he believed the sea to be the grand source of lightning, and built up an imposing fabric of conclusions upon the belief; but he did not hesitate afterwards to admit that he had embraced this opinion too hastily. The same thing is true of the opinion that he held for a time, that the progress of a ship westward, across the Atlantic, is retarded by the diurnal motion of the earth. He supposed that the melting brought about by the action of lightning was a cold fusion until holes burnt in a floor by portions of a molten bell wire convinced him that this was not so. I was too easily led into that error [he said] by accounts given even in philosophical books, and from remote ages downwards, of melting money in purses, swords in scabbards, etc. without burning the inflammable matters that were so near those melted metals. But men are, in general, such careless observers, that a philosopher can not be too much on his guard in crediting their relations of things extraordinary, and should never build an hypothesis on anything but clear facts and experiments, or it will be in danger of soon falling, as this does, like a house of cards. In one of his letters to Collinson, he declared that, even though future discoveries should prove that certain conjectures of his were not wholly right, yet they ought in the meantime to be of some use by stirring up the curious to make more experiments and occasion more exact disquisitions. Following out the same thought in another letter to Collinson he concluded: "You are at liberty to communicate this paper to whom you please; it being of more importance that knowledge should increase, than that your friend should be thought an accurate philosopher." In a letter to John Lining, in which he described the experiment from which Cavendish deduced the law of which we have spoken, he observed: