ON THE MECHANICAL EQUIVALENT or HEAT 



407 



It is to be noted that, although it is theoretically possible to measure 

 magnetic energy in absolute units, yet it cannot be done practically with 

 any great accuracy, and is thus useless in the determination of the 

 equivalent. It could be thus left out from the direct methods without 

 harm, as also out of the next to last term in the indirect methods. 



TABLE XXV. SYNOPSIS OF METHODS FOR OBTAINING THE 

 MECHANICAL EQUIVALENT OF HBAT. 



j Mechanical Energy 

 J. Gravltatlon 



4 ft. Heat, Electric Energy . 



y. Heat, Magnetic Energy 



1. Reversible process 



I 2. Irreversible 

 cess 



pro- 



l. Reversible process 



2. Irreversible 

 cess 



pro- 



f a. Expansion or compression ac- 

 cording to adlabatlc curve. 

 6. Expansion or compression ac- 

 cording to Isothermal curve. 



c. Expansion or compression ac- 



cording to any curve with re- 

 generator. 



d. Electro-magnetic engine driven 



by thermo-electric pile In a 

 circuit of no resistance. 



a. Friction, percussion, etc. 



6. Heat from magneto-electric cur- 

 rents, or electric machine. 



a. Thermo-electric currents. 



ft. Pyro-electric phenomena (prob- 

 ably). 



a. Heating of wire by current, or 

 heat produced by discharge 

 of electric battery. 



( a. Thermo-electric current mag- 



1. Reversible process '. netizlng a magnet in a circuit 



of no resistance. 



2. Irreversible pro- ( a. Heating of magnet when de- 



cess I magnetized. 



a. Radiant Energy, Heat 



(Radiant energy absorbed 

 by blackened eurface.) 



0. Chemical Energy, Heat 



(Combustion, etc.) 



y. Capillary energy, Heat 



(Heat produced when a liq- 

 uid Is absorbed by a po- 

 rous solid.) 



S. Electrical energy, Heat 



(Heat generated in a wire 

 by an electrical current.) 



e. Magnetic Energy, Heat 



(Heat generated on demag- 

 netizing a magnet.) 



Gravitation Energy, Heat 

 (Heat generated by a tail- 

 ing body.) 



Crooke's radiometer. 

 Thermo-electric pile. 

 Thermo-electric pile with electro- 

 magnet In circuit. 



1. Cannon. 



2. Electro-magnet machine run by 



galv. battery. 

 Current from battery. 

 Electro-magnet magnetized by a 



battery current. 



a. Mechanical Energy. 



5. Electrical " 



c. Magnetic " 



d. Gravitation " 



a. Mechanical Energy 



6. Electrical " 



c. Magnetic " ? 



d. Gravitation " 



a. Mechanical Energy. Movement of liquid by capillarity. 

 . _. j Electrical currents from capillary 



" *' { action at surface of mercury. 



c. Magnetic " 



d. Gravitation " Raising of liquid by capillarity. 



agneto-electric or electro-mag- 

 netic machine. Electric at- 

 traction. 

 Electro-magnet. 



a. Mechanical Energy 



6. Magnetic " 

 c. Gravitation " 



j M 



a. Mechanical Energy 



6. Electrical 

 c. Gravitation 



Armature attracted by a perma- 

 nent Magnet. 



Induced current on demagnetizing 

 a magnet. 



a. Mechanical Energy. J Velocity Imparted to a falling 

 6. Electrical " I body. 



c. Magnetic 



