HEAT OR CALORIC. 35 



SEC. II. HEAT OR CAIA)RiC. 



GENERAL NATURE OF THIS POWER. 



1. The sensation produced in us, by a hot body, ive attribute to a 

 power which we call heat meaning that which is the cause of the 

 sensation. 



2. This cause is unknown but, as that which excites in us the 

 sensation of heat, produces at the same time, expansion in all the 

 bodies, with which it communicates, both effects are attributed to 

 one cause. 



3. The cause of heat and of expansion are therefore assumed to be 

 one and the same, and this unknown cause is called, in modern chemi- 

 cal language, Caloric; (Calor, Lat. Calorique, Fr.)* but to avoid 

 pedantry and repetition, the terms, HEAT and CALORIC, are both 

 occasionally used to denote the cause in question. 



4. Our sensations of heat and cold are dependent, principally, on 

 the motion of Caloric. 



(a.) When it is entering our bodies, we feel warm or hot ; when 

 it is leaving us, we feel cool or cold, as the process is in either case 

 more or less rapid. 



(b.) More accurately speaking we feel hot, or cold, according 

 as the quantity of heat, that enters or leaves us, is greater or less than 

 the average quantity to which we are accustomed for heat is always 

 flowing from us during life, and generally more rapidly than it is re- 

 ceived, from without, as our natural temperature is higher than the aver- 

 age temperature of the air. If therefore, we lose more heat than we 

 are, on the whole accustomed to lose, we feel cold, and the reverse. 



(c.) Cold is merely a negation of heat. 



The same person may feel heat and cold in different parts of his 

 frame at the same time; for instance, by dipping at the same mo- 

 ment, one hand in cold, the other in hot water ; or, by laying, simul- 



* The new nomenclature of Chemistry had its origin in France. 



The necessity of this reform arose from the progress of discovery. The language 

 of Chemistry had become both erroneous and imperfect. Some newly discovered 

 bodies had no names; many old names were false, and others barharous or ridicu- 

 lous. The period was about 1785, at which time the new nomenclature wa* per- 

 fected. The p'incipal agents in this reform were Lavoisier, Fourcroy, Morveau, 

 and Berthollet. Movveau proposed the measure in 1782. The nomenclature will 

 be explained in detail, as the terms occur. See Jour, de Phy. Tome 10. p, 370. 



My much respected teacher, Professor HOPE, of the University of Edinburgh, 

 at first colleague, and afterwards successor to Dr. Black, was perfectly familiar 

 with the illustrious LAVOISIER, in the later periods of his life, andwas fully ac- 

 quainted with his discoveries and researches. Dr. Hope returned from Paris to 

 Scotland, strongly imbued with the new views, and was the first public teacher in 

 Britain who made them known, and who adopted the new nomenclature in his lec- 

 tures. I had this from him when I was his pupil. 



The late Dr. Pearson, of London, was also one of the first who promulgated the 

 modern nomenclature and discoveries in Great Britain. 



