NOVUM ORGANUM. 255 



Postquam autem fuerit vitrum illud collocatum ut diximus, 

 recipiet et contrahet se aer (qui dilatatus erat per calefactionem), 

 post moram sufficientem pro extinctione illius ascititii caloris, 

 ad talem extensionem sive dimensionem qualis erit aeris am- 

 bientis aut communis tune ternporis quando immittitur vitrum, 

 atque attrahet aquam in sursum ad hujusmodi mensuram. 

 Debet autem appendi charta angusta et oblonga, et gradibus 

 (quot libuerit) interstincta. Videbis autem, prout tempestas 

 diei incalescit aut frigescit, aerem se contrahere in angustius 

 per frigidum et extendere se in latius per calidum ; id quod 

 conspicietur per aquam ascendentem quando contrahitur aer, 

 et descendentem sive depressum quando dilatatur aer. Sen- 

 sus autem aeris, quatenus ad calidum et frigidum, tarn sub- 

 tilis est et exquisitus ut facultatem tactus humani multum 

 superet ; adeo ut solis radius aliquis, aut calor anhelitus, multo 

 magis calor manus, super vitri summitatem positus, statim 

 deprimat aquam manifesto. l Attamen existimamus spiritum 

 animalium magis adhuc exquisitum sensum habere calidi et 

 frigidi, nisi quod a mole corporea impediatur et hebetetur. 



39. Post aerem, existimamus corpora esse maxime sensitiva 

 caloris ea quae a frigore recenter immutata sint et compressa, 

 qualia sunt nix et glacies ; ea enim leni aliquo tepore solvi 

 incipiunt et colliquari. Post ilia sequitur fortasse argentum 

 vivum. Post illud sequuntur corpora pinguia, ut oleum, buty- 

 rum, et similia ; deinde lignum ; deinde aqua ; postremo lapides 



1 In consequence of this description of the Vitrum Calendare, the invention of the 

 Thermometer has been ascribed to Bacon ; but without good reason. Fludd was 

 the first to publish an account of the Thermometer ; but Nelli says, and (admitting 

 his authorities) truly, that Galileo's invention was anterior to any publication of 

 Fludd's. Nelli speaks of a letter preserved in the library of his family " in copia," 

 which Castelli addressed to Cesarina in 1638. Castelli says that, more than thirty- 

 five years before, Galileo had shown him an experiment which he describes ; namely, 

 the rise of the water into an inverted tube with a bulb at one extremity, when the 

 open end of the tube is put into a vessel of water, and goes on, " del quale effetto il 

 medesimo Signor Galileo si era servito per fabbricare un Istromento da esaminare i 

 gradi del caldo e del freddo." Thus far Castelli ; but how long after the original ex- 

 periment the instrument was made, does not appear from his statement. Nelli also 

 refers to Viviani's Life of Galileo, wherein it is said that Galileo invented the Ther- 

 mometer between 1593 and 1597. It has not, I think, been remarked that the rise 

 of water under the circumstances of Galileo's original experiment had already been 

 described in Porta's Natural Magic; though, as is usually the case with Porta, one 

 cannot be sure whether he had ever actually seen it. " Possumus etiam solo calore 

 aquam ascendere facere. Sit dolium supra turrim, vel ligneum, vel argillaceum aut 

 sereum, quod melius erit, et canalem habeat in medio, qui descendat inferius usque ad 

 aquam, et in ea submersus sit, sed adglutinatus, ne respiret. Calefiat vas superius 

 vel sole vel igne, nam aer, qui in alvo continetur, rarefit et foras prolubitur, unde 

 aquam in bullas tumere videbimus, mox absentia solis ubi vas refrigescit, aer conden- 

 satur, et quum non sufflciat inclusus aer vacuum replere, accersitur aqua et ascendit 

 supra." Porta's Magic, book xix. chap. 4. 



