38. The third part of the Instauratio Magna was to comprise an entire natural history, diligently and scrupulously collected from experience of every kind; including under that name of natural history everything wherein the art of man has been employed on natural substances either for practice or experiment; no method of reasoning being sufficient to guide us to truth as to natural things, if they are not themselves clearly and exactly apprehended. It is unnecessary to observe that very little of this immense chart of nature could be traced by the hand of Bacon, or in his time. His Centuries of Natural History, containing about one thousand observed facts and experiments, are a very slender contribution towards such a description of universal nature as he contemplated; these form no part of the Instauratio Magna, and had been compiled before. But he enumerates one hundred and thirty particular histories which ought to be drawn up for his great work. A few of these he has given in a sort of skeleton, as samples rather of the method of collecting facts, than of the facts themselves; namely, the History of Winds, of Life and Death, of Density and Rarity, of Sound and Hearing. |Fourth part: Scala Intellectûs.| 39. The fourth part, called Scala Intellectûs, is also wanting with the exception of a very few introductory pages. “By these tables,” says Bacon, “we mean not such examples as we subjoin to the several rules of our method, but types and models, which place before our eyes the entire process of the mind in the discovery of truth, selecting various and remarkable instances.”[190] These he compares to the diagrams of geometry, by attending to which the steps of the demonstration become perspicuous. Though the great brevity of his language in this place renders it rather difficult to see clearly what he understood by these models, some light appears to be thrown on this passage by one in the treatise De Augmentis, where he enumerates among the desiderata of logic what he calls traditio lampadis, or a delivery of any science or particular truth according to the order wherein it was discovered.[191] “The methods of geometers,” he there says, “have some resemblance to this art;” which is not, however, the case as to the synthetical geometry with which we are generally conversant. It is the history of analytical investigation, and many beautiful illustrations of it have been given since the days of Bacon in all subjects to which that method of inquiry has been applied.