MATTER 



93 



Body, &c., but all are inadequate. The reason is 

 simply that we do not yet know what Matter is, 

 and it is probable that we shall never l>e able to 

 obtain an exact and complete conception of its 

 true nature. Metaphysicians differ among them- 

 selves more perhaps on this subject than on almost 

 any other. Some of them deny altogether the 

 possibility of objective existence. Many, how- 

 ever, tell us that ' Matter is whatever can be 

 perceived by the senses.' Others vary the phrase 

 slightly, anil call mattera ' Permanent possibility of 

 sensation.' Hegel defines it as ' Nature self-exter- 

 nality in its most universal form, with a tendency 

 to self-internality or individuation shown in the 

 ni-u- df gravitation" ! Scientific men can, as yet, 

 define matter only by some of its properties. One 

 of their favourite definitions is Matter is what can 

 orciipy space. Another is that which possesses 

 inertia. Again, it may 1* regarded as the vehicle 

 of Energy (f[. v. ), inasmuch as energy is never 

 found except ill association with matter. liut the 

 scientific man, though confessing that none of his 

 definitions can be adequate, knows that each of 

 them expresses some part of the truth : and he 

 also knows that the metaphysical definitions cited 

 above (so far at least as they are intelligible) are 

 erroneous. For it is by the senses alone that we 

 know of the existence of energy, and energy is 

 certainly not matter. Again, the notion of Force 

 (q.v.) is entirely sense-suggested, and force is not 

 matter has not even objective existence. 



But, though the ultimate nature of matter is un- 

 known, we already know much aliout its structure 

 and properties, as well as almut what ( for the present 

 at least) we must call its various kinds. To a brief 

 sketch of these the present article is devoted. 

 Beside that unique and all-pervading species of 

 matter which we call the Ether (q.v.), which cer- 

 tainly satisfies the scientific definitions quoted 

 aliove, but about which we know little more, we 

 have what is called gross or ordinary matter. 

 This we find in two forms, solid or Huid. These 

 are sharply (HctiogttWiad from one another by their 

 elastic properties. For, while solids (as a rule) 

 possess, in a more or less imperfect degree, elas- 

 ticity alike of bulk and of form, Iliiids possess the 

 first in perfection and are alisolutcly devoid of the 

 second. Fluids again are divided into liquids, 

 vapours, and gases. These distinctions, in the case 

 of any one substance, as well as that between 

 solids and fluids, are found to dei>end mainly upon 

 temperature. 



The existence of the gaseous state, with its very 

 special features, has enabled us to obtain great 

 insight into the structure of matter. For experi- 

 ment has assured as that a gas is not a continuous 

 sulistance, but an assemlilage of an enormous num- 

 ber of perfectly distinct and independent particles, 

 each of which moves freely till it collides with 

 another, and thus some eight thousand mil linn 

 times per second has its motion completely changed. 

 The iinmlier of such separate particles in a single 

 cubic inch of air contains twenty-one figures i.e. 

 is expressed in hundreds of trillions. Yet they are 

 very fur from filling that space. Their total bulk 

 prohahly amounts to less than the five-hundredth 

 part of it. We are unable to discover any differ- 

 ences among the particles of the oxygen group, or 

 among those of the nitrogen : though, by delicate 

 -i'S not involving chemistry, we can detect a 

 difference tatween the properties of an oxygen and 

 of a nitrogen particle. As all known simple sub- 

 stances can l>e brought into the gaseous form, we 

 have a proof that every simple solid or fluid must 

 In- Imilt, up of particles absolutely equal to one 

 another. We figure to ourselves what we call 

 molecular forces (see article MOLECULE) as 

 the cause of the agglomeration, and ascribe the 



various states of solid, liquid, vapour, and gas in 

 any one substance to the greater or less relative 

 activity of the molecular forces (attractive) 

 and of the thermal motions (disjunctive or dis- 

 persive). The modern kinetic theory of Gases 

 (q.v.) has thus enabled us to account for at least 

 the more simple of their physical properties, such 

 as the experimental relations among pressure, 

 volume, and temperature, known as the laws of 

 Boyle and Charles; and the equality of numbers 

 of particles in a cubic inch of each of two gases at 

 the same temperature and pressure, known as 

 Avogadro's Law; as well as to study the mechanism 

 of gaseous viscosity, diffusion, and heat-conduction. 

 Much has already l>een done towards the explana- 

 tion of the 'critical temperature' and the vapour 

 state with its relation to that of liquid, and further 

 progress may soon be expected. On the other 

 Iiand, a great deal of information as to the liquid 

 aggregate has been obtained from experiments on 

 Capillarity (<J- V -) and Compressibility (q.v. ); and 

 as to the solid aggregate from its elastic properties, 

 &c. , but specially from the forms of crystals (see 

 CRYSTALLOGRAPHY ). Besides the molecular forces 

 mentioned al>ove, which are generally understood 

 as those exerted between particles of the same kind, 

 we have thoseof Chemical Affinity, which are exerted 

 between any two particles of different kinds. Physi- 

 cal experiments, following those of Andrews on the 

 compressibility of gaseous mixtures, promise to 

 give us much information on this subject ; but, in 

 the main, it is at present more immediately in the 

 domain of Chemistry (q.v.), tn which we must refer 

 for the discussion of Atomic Weights, Combining 

 Volumes, Valency, &c. 



Beyond the state of equal independent particles, 

 as in a simple gas, we know as yet nothing. Many 

 of the properties of the individual particles can be 

 obtained from the properties of the aggregate, 

 others by the help of Spectrum Analysis (q.v.). 

 But in answer to the question, Do the particles 

 of different simple substances consist of one and 

 the same ultimate material, or no? intensely attrac- 

 tive as it is, we have absolutely nothing to say. 

 So it is with the question, Are these particles 

 themselves further divisible, or are they atoms? 

 Atoms (q.v.), whether Lucretian or Vortical, are 

 not even proved to exist. We must, therefore, 

 in further discussing the subject, content ourselves 

 with a few brief statements as to the Properties 

 of Matter. 



One of the most remarkable of these, what has 

 been called Conservation of Matter, is the experi- 

 mentally ascertained fact that no.process at the 

 command of man can destroy even a single particle 

 of matter. Still less can it create a new one. It is 

 on this definite basis that the great science of 

 chemistry has l>een securely built. The Balance 

 (q.v.), used to determine quantity of matter with 

 the utmost precision, is its chief instrument. And 

 this attribute of unchangeable quantity furnishes 

 the most powerful of the arguments for the objec- 

 tive reality of matter. 



Quantity of matter, or mass, as it is technic- 

 ally called, is measured by Inertia, which (as 

 expressed in Newton's First Law of Motion ) may 

 be looked on as the fundamental property of 

 matter. For it is a property possessed by every 

 body, even a particle, in itself, and independently of 

 the vicinity or even the existence of any other 

 body. It is in virtue of its inertia that a body can 

 possess energy of motion, and that work is required 

 in order to set in motion even the smallest particle 

 of matter. Similarly, until it can transfer its 

 energy to some other body, a moving mass must 

 continue to move. 



Next in order of simplicity to inertia, which, as 

 we have seen, is a property of every single particle, 



