CHAP. XII.] HISTORY OF DYNAMICS. 397 



all the effects of putting in more or less of the iron core, or 

 more or less resistance and Leyden jars in either circuit. 



I have also been making a clay model of Prof. W. Gibb's 

 thermodynamic surface, representing the relations of the solid 

 liquid and gaseous states, and the different paths by which a 

 body may get from the one to the other. Your afft. friend, 



J. CLERK MAXWELL. 



To W. GARNETT, Esq. 1 



Gkrilair, 4th January 1877. 



By all means take the Groves and coils for your lecture. 

 Are you aware that the electric flash is entirely due to the 

 resinous particles of electricity ? This is well known on the 

 stage, where they blow the particles through a tube over a 

 candle to make stage lightning. The vitreous electricity has 

 nothing to do with it, as you may prove by using pounded 

 glass. 



In a letter to Mr. Garnett, dated Glenlair, 9th 

 July 1877, Professor Maxwell gave the following 

 suggestions respecting a projected article on Dynamics, 

 and the letter, like those which follow it, is a good 

 illustration of the help he was constantly rendering to 

 his students and others who asked his advice : 



I think it a pity that the old historical word Dynamics 

 should, for mere considerations of time, be split up into 

 Kinematics, Kinetics, and Statics. With respect to the 

 divisions of the subject, I think they fall thus : 



1. Early attempts at founding the science, ancient 

 Kinematics (mechanical description of curves, etc.) generally 

 correct. 



Ancient Statics. Archimedes. 



Modem Dynamics. Galileo, first founder. Descartes, 

 good up to Kinematics and Statics, failed in 

 Kinetics. 



1 See p. 370. 



