HISTORY OF DYNAMICAL THEORY OF HEAT. 207 



since the enunciation of atomic doctrines by the old Greek philoso- 

 phers and from their great suggestiveness the speculations of re- 

 flective minds have wandered over wellnigh every imaginable hy- 

 pothesis, and approximated with greater or less minuteness to the 

 views which are admitted now, and which we think to be supported 

 by experiment. Thus, as a case in point, we may refer to Galileo, 1 

 whose resource of observation could have scarcely been superior to 

 Archimedes's, and who would seem to have conceived of an increase 

 of heat as only a more elementary condition of material substance, in 

 which .the more or less considerable destruction of molecular bonds 

 allowed the individual particles of a body to move among themselves 

 with a more unconstrained vibration. 



But very few among the countless suppositions which we might 

 thus succeed in raking up, however curious or predictive in them- 

 selves, would have the slightest bearing on our present subject. De- 

 veloped only to the extent demanded by the superiority of the scho- 

 lastic mind, they would be found in general mere arbitrary, whimsical 

 assertions ; untried and unsupported by critically-devised experiments. 

 With the reformation of philosophy does our historical sketch then 

 properly begin, and, moreover, with Lord Bacon as its founder ; for, 

 in illustrating the proper method of establishing a philosophical doc- 

 trine, he forever identified himself with the dynamic theory, by show- 

 ing that the most comprehensive explanations were afforded by con- 

 sidering heat to be an intestine motion of the constituent particles of a 

 body. Systematically reviewing the known properties and effects of 

 heat the only practicable course open to him he concluded in the 

 following memorable and oft-quoted passages : 2 



" Atque htec sit Prima Vindemiatio, sive Interpretatio inchoata de Forma 

 Calidi, facta per Permissionem Intellectus. 



" Ex Vindemiatione autem ista Prima, Forma sive definitio vera Caloris (ejus 

 qui est in ordine ad universum), non relativus tantummodo ad sensum talis est, 

 brevi verborum ,complexu : Color est motus expanmw, cohibitets, et nitens per 

 partes minores." 



We find, therefore, in older writings, the first considerable support 

 of this doctrine attributed to Bacon ; and it must be conceded that to 

 the power and vividness with which he portrayed his conception of 

 this agent was due in a great measure the tenacity with which it was 

 afterward, from time to time, brought forward and upheld. 



The subsequent supporters of this view, though not perhaps most 

 numerous, comprised by far the most distinguished and profound 

 philosophers of their time, their writings furnishing many remarkable 

 anticipations of heat-theory as now received. 



1 " Opere di Galileo Galilei," torn, ii., p. 505, et seq. 



2 " Novum Organum," lib. sec., aphorism 20. Spedding and Ellis's translation, vol. iv., 

 p. 154. 



