238 LECTURE V. 



Brodie, which I have mentioned in the 

 first lecture of this year, seem satisfactorily 

 to show, that the transitions of colour, 

 which are produced in the blood by respira- 

 tion and circulation, are not of themselves 

 alone adequate to occasion a change of tem- 

 perature. I am at a loss to know what 

 chemists now think respecting heat, whe- 

 ther they consider it to be a distinct species 

 of matter, or mere motion and vibration. 

 Among the curious revolutions which this 

 age has produced, those of chemical opi- 

 nions have a fair claim to distinction. To 

 show which, I may mention, that a lady * on 

 her first marriage, was wedded to that sci- 

 entific champion who finally overthrew the 

 dominion of phlogiston, and established in 

 its stead the empire of caloric; and after his 

 decease, on her second nuptials, was uni- 

 ted to the man, who vainly supposed he 

 had subverted the rule of caloric, and re- 

 stored the antient but long banished dy- 

 nasty of motion and vibration. In this 

 state of perplexity, I cannot advance with 



* Madame LaToisier, who afterwards married Count 

 Ruraford. 



