NOVUM ORGANUM. 327 



Verum non solum quasrenda est mcnsura motuum et actio 

 num simpliciter, sed multo magis comparative : id enim eximii 

 est usus, et ad plurima spectat. Atque videmus flammam ali- 

 cujus tormenti ignei citius cerni, quam sonitus audiatur ; licet 

 necesse sit pilam prius ae'rem percutere, quam flamma quse pone 

 erat exire potuerit ; fieri hoc autem propter velociorem trans- 

 actionem motus lucis, quam soni. Videmus etiam species visi- 

 biles a visu citius excipi quam dimitti ; unde fit quod nervi 

 fidium, digito impulsi, duplicentur aut triplicentur quoad spe- 

 ciem, quia species nova recipitur, antequam prior demittatur ; 

 ex quo etiam fit, ut annuli rotati videantur globosi, et fax 

 ardens, noctu velociter portata, conspiciatur caudata. 1 Etiam 

 ex hoc fundamento inaequalitatis motuum quoad velocitatem, 

 excogitavit Galilaeus causam fluxus et refluxus mar is ; rotante 

 terra velocius, aquis tardius ; ideoque accumulantibus se aquis 

 in sursum, et deinde per vices se remittentibus in deorsum, ut 

 demonstratur in vase aquae incitatius movente. 2 Sed hoc 

 commentus est concesso non concessibili (quod terra nempe 

 moveatur), ac etiam non bene informatus de oceani motu sex- 

 horario. 



At exemplum hujus rei de qua agitur, videlicet de compa- 



time when we see it there, in other words, if the image took any time in coming to 

 the eye, this very thing does actually happen as often as the star is hidden by a cloud 

 or dimmed by a vapour : the species, to use his own word, are intercepted or con- 

 fused. If, indeed, the force of the rays were diminished, and this I suppose would be 

 one consequence of diminished velocity, the thing would happen more frequently, be- 

 cause there would be more obstructions which they could not overcome : they would 

 be intercepted or confused by media which they now pass through. But the force 

 being the same, and the stream continuous, the time of passage could make no differ- 

 ence in this respect. In another respect, namely the facility of observation, it would 

 make a very great difference ; and it is remarked by Brinkley that, if the velocity of 

 light had been much less than it is, astronomy would have been all but an impossible 

 science. But that is another matter. J. S. 



1 Of the phenomena which he here enumerates Bacon undoubtedly gives the right 

 explanation, though in the case of vibrating strings his explanation is not altogether 

 complete. The distinct or quasi-distinct images to which he refers correspond to 

 limiting positions of the- vibrating string. 



2 This account of Galileo's theory of the tides is inaccurate. In this theory the 

 tides are caused by the varying velocity of different points of the earth's surface, 

 arising from the composition of the earth's two motions, namely that about its axis, 

 and that in its orbit. Bacon does not seem to have perceived that both these mo- 

 tions are essential to the explanation. That the earth's being in motion might be 

 the cause of the tides, had been suggested before the time of Galileo by Caesalpinus in 

 the Quccstimes Peripatetics, iii. 5. It is odd that Patritius, in giving an account of all 

 the theories which had in his time been devised to explain the cause of the tides (see 

 his Pancosmia, 1. 28.), does not mention Caesalpinus's, though it was published some 

 years before his own work. Galileo perhaps alludes to Csesalpinus in his letter to 

 Cardinal Orsino, dated 8tb January, 1616. See, for remarks on Caesalpinus's doctrine, 

 the Problemata Marina w i Casmann, published in 1596. Casmann's own theory is 

 that of expansion. 



Y 4 



