(2) they must also allow of the transmission of light, such as is being transmitted through these windows, to be reflected or absorbed by the opposite wall;
(3) of the gravitation of matter, as when I drop this ball;
(4) of the (limited) cohesion of matter, on which the strength of our structures depend. Thus I can break this stick of sealing-wax, and when I warm the ends and bring them together, when cold it is as strong as before;
(5) of the elasticity of matter, as shown by the continued vibration of this spring;
(6) of the limited friction of matter, as is shown by the weight resting on the inclined plane until the inclination reaches a certain angle, when it slides down at an accelerating rate;
(7) of the viscosity of matter, as is shown by putting oil on the inclined plane, when the weight slides down slowly and at a steady rate;
(8) of the electric and magnetic properties of matter, shown by the absence of any affinity of the stick of sealing-wax for the paper until it is rubbed by silk, when it at once picks up the paper;
(9) of the freedoms and mutual constraints
