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edebat. Id ab aëris tepefacti extensione, quæ principium motus dare potuit, factum fuisse verisimile est; cum certum sit aërem, vel exigui admodum caloris contactu lacessitum, expansionem statim moliri.
Verum ad magis accuratam expansionis aëris notitiam, ad vesicam illam sensibilem versi, vitrum accepimus vacuum (scilicet aëre solo impletum); ei pileum illum ex vesica (de quo jam antea locuti sumus) imposuimus. Vitro autem super ignem imposito, celerius et minore calore se extendebat aër, quam aqua aut spiritus vini ; sed expansione non admodum ampla. Hanc enim proportionem ferebat: si vesica ex semisse minoris contenti erat quam vitrum ipsum, aër illam fortiter sane et plene inflabat; ad majorem expansionem non facile adscendebat; foramine autem in summitate vesicæ, dum inflaretur, facto, nullum exibat corpus visibile.
DESCRIPTIO GLOBI INTELLECTUALIS.
This tract, published by Gruter in 1653, must have been written about 1612. This follows from what is said of the new star in Cygnus', which was first observed in 1600. It is therefore intermediate in date between the Advancement of Learning and the De Augmentis ; and though on a larger scale than either, it is to be referred to the same division of Bacon's writings. The design of all three is the same, namely, a survey of the existing state of knowledge. The commendation of learning which forms the first book of the other two works being in this one omitted, it commences with the tripartite division of knowledge which Bacon founded on the corresponding division of the faculties of man-memory, imagination, and reason. History, which corresponds to memory, is here as in the De Augmentis primarily divided into natural and civil, whereas in the Advancement the primary division of history is quadripartite, literary and ecclesiastical history being made co-ordinate with civil history, instead of being as here subordinated to it.
The divisions of natural history are then stated, and are the same as in the De Augmentis ; and the remainder of the tract relates to one of these divisions, namely the history of things
Stella nova in pectore Cygni . , jam per duodecim annos integros duravit.
celestial, or in other words to astronomy. The problems which it should consider, and the manner in which they ought to be solved, are treated of at some length; but even with respect to astronomy much which it is proposed to do is left undone, the whole tract being merely a fragment.
Bacon has nowhere else spoken so largely of astronomy; the reason of which apparently is, that he was writing just after Galileo's discoveries had been made known in the Sydereus Nuncius, published in 1611; a circumstance which makes the Descriptio Globi Intellectualis one of the most interesting of his minor writings. The oracles of his mind were in this case evoked by the contemplation, not of old errors, but of new truths.
The Thema Cæli, which contains a provisional statement of his own astronomical opinions, is immediately connected with the astronomical part of the Descriptio Globi Intellectualis. They are clearly of the same date, and form in reality but one work.
In the De Augmentis Bacon has expressed the same general views on the subject of astronomy as in these tracts; and they are in truth views which it was natural for a man not well versed in the phenomena of the science to entertain and to promulgate. What had been done by the old astronomers seemed to him full of useless subtleties and merely mathematical conceptions; men therefore were to be exhorted to cast all these aside, and to study the phenomena of the heavens independently of arbitrary hypotheses. Let us first obtain an accurate knowledge of the phenomena, and then begin to search out their real causes. Orbs, eccentrics, and epicycles must not stand between the astronomer and the facts with which he has to deal. In this language, which had been held by others, there is something not wholly untrue; yet the counsel which it contains would, if it could have been followed, have put an end to the progress of astronomical science. Let us obtain an accurate knowledge of the phenomena this no doubt is necessary, but then how is it to be done? To say that instead of trying to resolve the motion of the planets into a combination of elementary circular motions, we ought to be content to save the appearances by means of spirals, is to no purpose unless we are prepared to give an accurate definition of the kind of spiral we mean. Failing this, a statement that the