NOVUM ORGANUM. 



267 



Quod vero ad Operativam attinet, eadem res est. Nam 

 designatio est tails ; Si in aliquo corpore naturali poteris ex- 

 citare motum ad se dilatandum aut expandendum ; eumgue 

 motum ita reprimere et in se vertere, ut dilatatio ilia non procedat 

 cequaliter, sed partim oblineat, partim retrudatur ; proculdubio 

 generates Calidum : non habita ratione, sive corpus illud sit 

 elementare (ut loquuntur) sive imbutum a coelestibus l ; sive 



luminosum sive opacum : sive tenue siy/e densum ; sive loca- 



,.^ . . ?fn* t'r-CjL (iiytf-dv. 



liter expansum sive mtra claustra dimensions primas conten- 



tum ; sive vergens ad dissolutionem sive manens in statu ; 

 sive animal, sive vegetabile, sive minerale, sive aqua, sive oleum, 

 sive aer, aut aliqua alia substantia quaecunque susceptiva motus 



source of this confusion I believe to be thaf, though Bacon saw reason to affirm 

 expansion to be the essence of the hot, yet he was perplexed by examples of two 

 kinds : (a) bodies which do not visibly expand when they are heated, e. g. red-hot 

 iron ; (j8) bodies which expand without becoming heated, e. g. compressed air when 

 relieved from pressure. For the first difficulty, it might have occurred to him that 

 the hot iron does expand, though not enough to be perceived (except by accurate 

 measurement) to do so ; and if he had followed the indication thus given, he might 

 have been the discoverer of a general and most important law. The difficulty which 

 the second class of phenomena creates ought to have prevented Bacon from assigning 

 expansion as the forma calidi, as being that which must always make a body hot, 

 and without which it could not become so. For it would be too liberal an interpre- 

 tation to say that the expressions " motus cohibitus et refraenatus," whereby the idea 

 of expansion is qualified, refer to a condition essential in the case of elastic fluids, 

 namely that the expansion in becoming heated is due to an increased elasticity, and not 

 to any decrease of external pressure. Even had the modification required by this class of 

 cases been introduced, there still remains that of liquids whose temperature is below that 

 of maximum density, which is altogether intractable. Of this phenomenon, however, 

 it would be unreasonable to expect Bacon to have known anything. But setting it 

 aside, if it were affirmed that Bacon, after having had a glimpse of the truth suggested 

 by some obvious phenomena, had then recourse, as he himself expresses it, to certain 

 " differentiae inanes " in order to save the phenomena, I think it would be hard to 

 dispute the truth of this censure. 



Nevei theless, of the matters contained in the investigation, there are several of con- 

 siderable interest, though, as has been said, they are not connected with the final result. 



The relation between heat and mechanical action has recently become the subject 

 of some very remarkable speculations, derived from the views suggested by S. Carnot 

 in his Reflections sur la Puissance Motrice du Feu. Two views have been pro- 

 pounded. In one (that of S. Carnot himself), mechanical action is regarded as con- 

 vertible with the transference from body to body of caloric. The other rejects the 

 notion of caloric (the substance of heat) altogether. On this view mechanical action 

 is convertible with the generation of heat ; i. e. the raising of a given quantity of a 

 given body from one given temperature to another. Both make use of the axiom " ex 

 nihilo nihil ; " and the conclusions thus obtained, especially in the second way of con- 

 sidering the subject, which I cannot doubt is the true one, are most remarkable, and 

 the more interesting because they are, so to speak, the interpretation of a maxim whose 

 truth is admitted a priori. 



1 That is, whether the body derive its properties from the primary qualities of the 

 elements, or be imbued with specific or virtual qualities through the influence of the 

 heavenly bo'dies. Thus St. Thomas says : " Sicut enim virtus calefaciendi et infrigidandi 

 est in igne et aqua consequens proprias eorum formas, et virtus, &c., actio intellect ua- 

 lis in homine consequens animam rationalcm, ita omnes virtutes et actiones mediorum 

 corporum transcendentes virtutes elementorum consequuntur eorum proprias formas, 

 et reducuntur sicut in altiora priucipia in virtutes corporum coelestium, et adhuc altius 

 in sub&tantias separatas." De occultis Opcrilmt, Natural. 



