Aether and Gravitation. William George Hooper
encloses the gas is caused by the total effect of the impact of the particles, and is proportional to the sum of their masses multiplied into the square of their velocities. If we halve the enclosed space, then we should double the number of impacts in a given time, so that the number of impacts is inversely as the volume of the gas. This is equivalent to the statement, that the pressure of a gas varies inversely as its volume, which is Boyle and Marriotte's Law.
Art. 37. Matter is Gravitative.--If there is one property which is essentially characteristic to all matter, it is that all matter is gravitative. To this rule there is no exception, as the universal Law of Attraction states that “every particle of matter attracts every other particle.” Thus, wherever in the whole universe there is a particle of matter of any kind or sort, whether such matter be solid, liquid, or gaseous, there the force of attraction will be exerted with a force proportionate to the mass of the particle, and inversely as the square of the distance between the attracted particles.
Gravitation, then, is a property which is essentially inherent in matter, and any substance which is termed matter, or fulfils the conditions that govern matter, must be gravitative, whatever other property it may, or may not, possess. Unless this be so, we should have a violation of the universal Law of Gravitation, which would cease at once to be a universal law, for instead of reading “every particle of matter attracts every other particle,” we should have to say that “some particles of matter attract some other particles,” which would be a violation of that universal law which, through the genius of Newton, has given to the universe an unity from the philosophical standpoint that it did not possess before.
Some matter may, or may not be elastic; it may, or may not be solid, or liquid, or gaseous; but there is this fact regarding matter which is absolutely undeniable, and that is, “All matter is gravitative.”
That this is true of each and all kinds of matter has been proved by direct experiment times without number, and the constant application of the law to all forms of matter is a fact observable from the phenomena incidental to every-day life. Astronomical observation teaches us also, that all stars, suns, planets, satellites, and comets are subject to this great Law of Gravitation, as indeed they must be if they are composed of matter. That they are all composed of exactly similar elements of which the earth is composed, has been proved again and again by spectroscopic analysis, which teaches that hydrogen, iron, and calcium, etc., are to be found in distant stars and nebulae, as they are equally to be found in the composition of the earth. Thus throughout the wide universe so far as observation and experiment can teach us, we learn that without any exception, everything that is termed matter is subject to this universal Law of Gravitation.
Art. 38. Matter possesses Density.--Density is that property of matter which decides the weight of a body per unit of volume.
The density of any substance may be shown in several ways. It may denote, first of all, the number of molecules in a given body. Let us take as an illustration, the case of air being forced into a vessel of a given size, say one cubic foot capacity. We will suppose that in such a vessel there are 1,000,000 molecules. If we pump in a quantity of air equal to the amount it contained at first, then it is obvious that we have doubled the number of molecules in the same vessel, and therefore we say we have doubled the density. Not only so, but the weight of the air in the vessel will have been doubled. Looked at from this standpoint, density means the number of molecules in unit volume such as a cubic inch, or cubic centimetre.
Again, as has already been shown in Art. 35, the different elements have different atomic weights. Thus an atom of carbon weighs twelve times as much as an atom of hydrogen, that is to say, there are twelve times as much matter by weight in an atom of carbon as there is in an atom of hydrogen, so that it would take twelve times as many hydrogen atoms to weigh a pound as compared with the number of atoms of carbon. This is only another way of stating that carbon has twelve times the density of hydrogen. If we compare lead and silver with hydrogen in the same way, we find that the density is 206 times and 107 times greater than that of hydrogen.
Thus, it may be seen, that all matter possesses density, and that that density depends partly upon its atomic constitution. If the molecule of matter is composed of atoms whose atomic weights are very large compared with that of hydrogen, as iron, silver, lead and gold, then the molecules will have a much greater density, than a molecule formed of oxygen and hydrogen, i.e. water. This property of the density of matter plays a most important part in the transmission of any kind of wave-motion.
Art. 39. Matter possesses Elasticity.--Matter possesses elasticity. Elasticity is that property of matter which enables all bodies to resume their original shape, when the pressure which has caused the alteration of shape has been removed.
For example, suppose an ivory ball be dropped upon a marble table, or any other hard surface. It will then rebound, and rise almost to the same height from which it was dropped. If the surface upon which it fell was first covered with blacklead, a circular spot of lead will be found on the ivory ball. From this fact, we arrive at the conclusion that when the ball came into contact with the table, at the moment of contact it was flattened, and then owing to its elasticity it rebounded into the air again.
Now the measure of the elasticity of a body is proportionate to the velocity of the wave-motion which it can transmit. A good illustration of the transmission of wave-motion may be shown with a number of ivory bagatelle or billiard balls. If eight or more of these be put in a row, all touching each other, and a single ball be placed about an inch or so away from the others in a straight line with them, then when the single ball is struck with a cue against the other eight, the motion of the single ball is transmitted by each one of the eight successively with such rapidity, that the end ball would be set in motion in a quicker time than a single ball would take to reach the end ball, if it had been free to move along without encountering any opposition.
It is a fact capable of demonstration, that the smaller the particle of matter, the greater will be its vibratory motion. Thus the particles of air are very, very small, and consequently air is found to be very elastic, and allows sound to be transmitted through it with comparatively great velocity, some sounds travelling at the rate of over 1000 feet per second.
A most important factor in determining the propagation of any wave-motion, through a gas or solid, is the relationship of the elasticity of the gas or solid to its density. Suffice to say, that the velocity of any wave-motion is determined by the relation of the elasticity to the density. For example, sound, which is a wave-motion of the air, can not only be transmitted through gaseous bodies as air, but also through liquids and solids. Sound travels faster through solids than through liquids, and faster through liquids than through gases. In liquids, the relation of the elasticity to density is greater than in air, and in solids the relation is greater still. Therefore sound travels much faster in liquids than in gases, and faster in solids than in liquids.
This is the reason why a train can be heard coming if the ear is put to the railway-line, when no indication of its approach is given to the ear by the atmosphere. Some examples of the velocities of sound through different substances are as follows--
| Gases O. C. feet | Liquids. feet | Solids feet |
|---|---|---|
| Air1090persec.Oxygen1040"" | Water4708persec.(8° C.).Alcohol4218""(20° C.). | Gold5717persec.Silver8553"" |
Art. 40. Matter possesses Inertia.--Inertia is that property of matter, by which matter cannot of itself alter, or change its state of motion, or of rest.
Newton's first law of motion states that a body at rest remains at rest until some force or motion acts upon it. If a stone be dropped from a balloon, the stone does not fall because of any property which it possesses, but because the force of gravity acts upon it. If it were possible to eliminate this force of gravity, then if there were no other force which could act upon the stone, it would remain suspended in space.
The inertia