630 Transactions of the American Institute. 



heat, is a new branch which has sprung up within the last twenty 

 years. The first question is : "What is force % Is force supernatural 

 — something residing in the human body, or is it something material : 

 Here is the key. It is a delusion to suppose that force is immaterial. 

 The moment we adopt that idea, we may suppose that it may be 

 communicated without contact. But modern biology, the science of 

 life, teaches us that what we call life and force are nothing but the 

 motion of matter. Force is matter in motion ; and where there is no 

 matter there is no force. Heat also is motion ; and in the steam- 

 engine the heat of the steam is converted into the motion of the 

 piston. 



"What does that expansion of the steam consist of? It is a new 

 theory that the molecules of gases are in rectillinear motion, impinging 

 upon the walls of the vessel, producing by their impact what we call the 

 pressure of the gases. In a solid, the motion is a vibration ; in a liquid, 

 it is a revolution of the molecules ; but in a gas, they are in rectilli- 

 near motion in all directions. This idea is strongly fortified by the 

 known fact of the diffusion of gases, which takes place with aston- 

 ishing rapidity, even when the lightest is above the heaviest. If we 

 raise the temperature, the velocity becomes greater, and of course the 

 pressure becomes greater ; and as the force is as the square of the 

 "velocity, this explains why the pressure increases so rapidly with 

 small increase of temperature. In moving the piston, the molecular 

 motion is changed to motion of the mass ; and in friction; the motion 

 of the mass is retransformed into molecular motion. 



So with the animal. Give an ox no food, and he cannot work. 

 The living animal is a most complicated machine. To produce 

 motion, the muscles must be contracted. That contraction must be 

 caused by the action of the nerve ; and that action of the nerve must 

 be caused by the will, the seat of which is in the brain. Experiments 

 have proved that every action is at the expense of matter. As you 

 Can have no motion of a machine, so you can have no motion of an 

 animal, without the expenditure of material. Every time I move my 

 arm, there is matter destroyed, or rather changed. Matter must be 

 supplied continually to the blood, to supply its place; and as the 

 waste is greater than the supply, when we are in action, it is neces- 

 sary to sleep for one-third of our lives, to give time for supplying the 

 waste; just as the engineer lets his engine stand still while he is 

 getting up steam. The nerve, in acting upon the muscle, and causing 

 it to contract, is consumed. The brain, where the will resides which 

 acts upon the nerve, is consumed. Without the consumption of 



