FOOTNOTES:

[1] See Maxwell, _Elementary Treatise on Electricity_ (Oxford, 1881),

p. 47.

[2] See Maxwell, _Treatise on Electricity and Magnetism_ (3rd ed.,

Oxford, 1892), vol. i. p. 80.

[3] Maxwell, Ibid. vol. i. S 74a; also _Electrical Researches of the

Hon. Henry Cavendish_, edited by J. Clerk Maxwell (Cambridge, 1879),

p. 104.

[4] Laplace (_Mec. Cel._ vol. i. ch. ii.) gave the first direct

demonstration that no function of the distance except the inverse

square can satisfy the condition that a uniform spherical shell

exerts no force on a particle within it.

[5] The solution of the problem of determining the distribution on an

ellipsoid of a fluid the particles of which repel each other with a

force inversely as the nth power of the distance was first given by

George Green (see Ferrer's edition of Green's _Collected Papers_, p.

119, 1871).

[6] See Thomson and Tait, _Treatise on Natural Philosophy_, S 519.

[7] See article "Electricity," _Encyclopaedia Britannica_ (9th

edition), vol. viii. p. 30. The reader is also referred to an article

by Lord Kelvin (_Reprint of Papers on Electrostatics and Magnetism_,

p. 178), entitled "Determination of the Distribution of Electricity

on a Circular Segment of a Plane, or Spherical Conducting Surface

under any given Influence," where another equivalent expression is

given for the capacity of an ellipsoid.

[8] See Maxwell, _Electricity and Magnetism_, vol. i. pp. 284-305

(3rd ed., 1892).

[9] It is an interesting fact that Cavendish measured capacity in

"globular inches," using as his unit the capacity of a metal ball, 1

in. in diameter. Hence multiplication of his values for capacities by

2.54 reduces them to E.S. units in the C.G.S. system. See _Elec.

Res._ p. 347.

[10] For fuller details of these methods of comparison of capacities

see J.A. Fleming, _A Handbook for the Electrical Laboratory and

Testing Room_, vol. ii. ch. ii. (London, 1903).

[11] See Fleming, _Handbook for the Electrical Laboratory_, vol. ii.

p. 130.

[12] Faraday, _Experimental Researches on Electricity_, vol. i. S

1252. For a very complete set of tables of dielectric constants of

solids, liquids and gases see A. Winkelmann, _Handbuch der Physik_,

vol. iv. pp. 98-148 (Breslau, 1905); also see Landolt and Bornstein's

_Tables of Physical Constants_ (Berlin, 1894).

[13] See the following papers by J.A. Fleming and James Dewar on

dielectric constants at low temperatures: "On the Dielectric Constant

of Liquid Oxygen and Liquid Air," _Proc. Roy. Soc._, 1897, 60, p.

360; "Note on the Dielectric Constant of Ice and Alcohol at very low

Temperatures," ib., 1897, 61, p. 2; "On the Dielectric Constants of

Pure Ice, Glycerine, Nitrobenzol and Ethylene Dibromide at and above

the Temperature of Liquid Air," id. ib. p. 316; "On the Dielectric

Constant of Certain Frozen Electrolytes at and above the Temperature

of Liquid Air," id. ib. p. 299--this paper describes the cone

condenser and methods used; "Further Observations on the Dielectric

Constants of Frozen Electrolytes at and above the Temperature of

Liquid Air," id. ib. p. 381; "The Dielectric Constants of Certain

Organic Bodies at and below the Temperature of Liquid Air," id. ib.

p. 358; "On the Dielectric Constants of Metallic Oxides dissolved or

suspended in Ice cooled to the Temperature of Liquid Air," id. ib. p.

368.

[14] See Faraday, _Experimental Researches_, vol. i. S 1245; R.H.A.

Kohlrausch, _Pogg. Ann._, 1854, 91; see also Maxwell, _Electricity

and Magnetism_, vol. i. S 327, who shows that a composite or

stratified dielectric composed of layers of materials of different

dielectric constants and resistivities would exhibit the property of

residual charge.

[15] Fleming and Ashton, "On a Model which imitates the behaviour of

Dielectrics." _Phil. Mag._, 1901 [6], 2, p. 228.

[16] The beginner is often puzzled by the constant appearance of the

factor 4[pi] in electrical theorems. It arises from the manner in

which the unit quantity of electricity is defined. The electric force

due to a point-charge q at a distance r is defined to be q/r^2, and

the total flux or induction through the sphere of radius r is

therefore 4[pi]q. If, however, the unit point charge were defined to

be that which produces a unit of electric flux through a

circumscribing spherical surface or the electric force at distance r

defined to be 1/4 [pi]r^2, many theorems would be enunciated in

simpler forms.

[17] See Maxwell, _Electricity and Magnetism_, vol. i. S 78b (2nd

ed.).

[18] Id. ib. vol. i. S 80. Coulomb proved the proportionality of

electric surface force to density, but the above numerical relation E

= 4[pi][sigma] was first established by Poisson.

[19] See Maxwell, _Electricity and Magnetism_, vol. i. S 99a (3rd

ed., 1892), where the expression in question is deduced as a

corollary of Green's theorem.

[20] See Lord Kelvin's _Papers on Electrostatics and Magnetism_, p.

144.

ELECTROTHERAPEUTICS, a general term for the use of electricity in

therapeutics, i.e. in the alleviation and cure of disease. Before the

different forms of medical treatment are dealt with, a few points in

connexion with the machines and currents, of special interest to the

medical reader, must first be given.

_Faradism._--For the battery required either for faradism or galvanism,

cells of the Leclanche type are the most satisfactory. Being dry they

can be carried in any position, are lighter, and there is no trouble

from the erosion of wires and binding screws, such as so often results

from wet cells. The best method of producing a smooth current in the

secondary coil is for the interruptor hammer to vibrate directly against

the iron core of the primary coil. For this it is best that the

interruptor be made of a piece of steel spring, as a high rate of

interruption can then be maintained, with a fairly smooth current in the

secondary coil. This form of interruptor necessitates that the iron core

be fixed, and variation in the primary induced current is arranged for

by slipping a brass tube more or less over the iron core, thus cutting

off the magnetic field from the primary coil. The secondary current

(that obtained from the secondary coil) can be varied by keeping the

secondary coil permanently fixed over the primary and varying the

strength of the primary current. Where, as suggested above, the iron

core is fixed, the primary and secondary induced currents will be at

their strongest when the brass tube is completely withdrawn. As there is

no simple means of measuring the strength of the faradic current, it is

best to start with a very weak current, testing it on the muscles of

one's own hand until these begin to contract and a definite sensory

effect is produced; the current can then be applied to the part, being

strengthened only very gradually.

_Galvanism._--For treatment by galvanism a large battery is needed, the

simplest form being known as a "patient's battery," consisting of a

variable number of dry cells arranged in series. The cells used are

those of Leclanche, with E.M.F. (or voltage) of 1.5 and an internal

resistance of .3 ohm. Thus the exact strength of the current is known;

the number of cells usually employed is 24, and when new give an E.M.F.

of about 36 volts. By using the formula C = E/R, where E is the voltage

of the battery, R the total resistance of battery, electrodes and the

patient's skin and tissues, and C the current in amperes, the number of

cells required for any particular current can be worked out. The

resistance of the patient's skin must be made as low as possible by

thoroughly wetting both skin and electrodes with sodium bicarbonate

solution, and keeping the electrodes in very close apposition to the

skin. A galvanometer is always fitted to the battery, usually of the

d'Arsonval type, with a shunt by means of which, on turning a screw,

nine-tenths of the inducing current can be short-circuited away, and the

solenoid only influenced by one-tenth of the current which is being used

on the patient. In districts where electric power is available the

continuous current can be used by means of a switchboard. A current of

much value for electrotherapeutic purposes is the sinusoidal current, by

which is meant an alternating current whose curve of electromotive

force, in both positive and negative phase, varies constantly and

smoothly in what is known as the sine curve. In those districts supplied

by an alternating current, the sinusoidal current can be obtained from

the mains by passing it through various transformers, but where the main

supply is the direct or constant current, a motor transformer is needed.

_Static Electricity._--For treatment by static electricity the Wimshurst

type of machine is the one most generally used. A number of electrodes

are required; thus for the application of sparks a brass ball and brass

roller electrode, for the "breeze" a single point and a multiple point

electrode, and another multiple point electrode in the form of a metal

cap that can be placed over the patient's head. The polarity of the

machine must always be tested, as either knob may become positive or

negative, though the polarity rarely changes when once the machine is in

action. The oldest method of subjecting a patient to electric influence

is that in which static electricity is employed. The patient is

insulated on a suitable platform and treated by means of charges and

discharges from an electrical machine. The effect is to increase the

regularity and frequency of the pulse, raise the blood pressure and

increase the action of the skin. The nervous system is quieted, sleep

being promoted, the patient often becoming drowsy during the

application. If while the patient is being treated a point electrode is

brought towards him he feels the sensation of a wind blowing from that

point; this is an electric breeze or brush discharge. The breeze is

negative if the patient is positively charged and vice versa. The

"breeze discharge" treatment is especially valuable in subduing pain of

the superficial cutaneous nerves, and also in the treatment of chronic

indolent ulcers. Quite recently this form of treatment has been applied

with much success to various skin lesions--psoriasis, eczema and

pruritus. Static electricity is also utilized for medical purposes by

means of "sparks," which are administered with a ball electrode, the

result being a sudden muscular contraction at the point of application.

The electrode must be rapidly withdrawn before a second spark has time

to leap across, as this is a severe form of treatment and must be

administered slowly. It is mainly employed for muscular stimulation, and

the contractions resulting from spark stimulation can be produced in

cases of nerve injury and degeneration, even when the muscles have lost

their reaction to faradism. The sensory stimulation of this form of

treatment is also strong, and is useful in hysterical anaesthesia and

functional paralysis. Where a milder sensory stimulation is required

friction can be used, the electrode being in the form of a metal roller

which is moved rapidly outside the patient's clothing over the spine or

other part to be treated. The clothing must be dry and of wool, and each

additional woollen layer intensifies the effect.

Another method of employing electricity at high potential is by the

employment of high frequency currents. There are two methods of

application: that in which brush discharges are made use of, with

undoubtedly good effects in many of the diseases affecting the surface

of the body, and that in which the currents of the solenoid are made to

traverse the patient directly. The physiological value of the latter

method is not certain, though one point of interest in connexion with it

is that whereas statical applications raise the blood pressure, high

frequency applications lower it. It has been used in the case of old

people with arterio-sclerosis, and the reduction of blood pressure

produced is said to have shown considerable permanence.

_The Faradic Current._--G.B. Duchenne was the first physician to make

use of the induced current for treatment, and the term "faradization" is

supposed to be due to him. But in his day the differences between the

two currents available, the primary and the secondary, were not worked

out, and they were used somewhat indiscriminately. Nowadays it is

generally accepted that the primary current should be used for the

stimulation of deep-lying organs, as stomach and intestines, &c., while

the secondary current is employed for stimulation of the limb muscles

and the cutaneous sensory nerves. The faradic current is also used as a

means of diagnosis for neuro-muscular conditions. When the interrupted

current is used to stimulate the skin over a motor nerve, all the

muscles supplied by that nerve are thrown into rapid tetanic

contraction, the contraction both beginning and ceasing sharply and

suddenly with the current. This is the normal reaction of the nerve to

faradism. If the muscle be wasted from disuse or some local cause

unconnected with its nerve-supply, the contraction is smaller, and both

arises and relaxes more slowly. But if the lesion lies in the nerve

itself, as in Bell's palsy, the muscles no longer show any response when

the nerve is stimulated, and this is known as the reaction of

degeneration in the nerve. It is usually preceded by a condition of

hyperexcitability. These results are applied to distinguish between

functional paralysis and that due to some organic lesion, as in the

former case the reaction of faradism will be as brisk as usual. Also at

the beginning of most cases of infantile paralysis many more groups of

muscles appear to be affected than ultimately prove to be, and faradism

enables the physician to distinguish between those groups of muscles

that are permanently paralysed owing to the destruction of their trophic

centre, and those muscles which are only temporarily inhibited from

shock, and which with proper treatment will later regain their full

power. In the testing of muscles electrically that point on the skin

which on stimulation gives the maximum contraction for that muscle is

known as the "motor point" for that muscle. It usually corresponds to

the entry of the motor nerve. Faradic treatment may be employed in the

weakness and emaciation depending on any long illness, rickets, anaemia,

&c. For these cases it is best to use the electric bath, the patient

being placed in warm water, and the two electrodes, one at the patient's

back and the other at his feet, being connected with the secondary coil.

The patient's general metabolism is stimulated, he eats and sleeps

better and soon begins to put on weight. This is especially beneficial

in severe cases of rickets. In the weakness and emaciation due to

neurasthenia, especially in those cases being treated by the Weir

Mitchell method (isolation, absolute confinement to bed, massage and

overfeeding), a similar faradic bath is a very helpful adjunct. In tabes

dorsalis faradic treatment will often diminish the anaesthesia and

numbness in the legs, with resulting benefit to the ataxy. Perhaps the

most beneficial use of the faradic current is in the treatment of

chronic constipation--especially that so frequently met with in young

women and due to deficient muscular power of the intestinal walls. In

long-standing cases the large intestine becomes permanently dilated, and

its muscular fibres so attenuated as to have no power over the

intestinal contents. But faradism causes contraction at the point of

stimulation, and the peristaltic wave thus started slowly progresses

along the bowel. All that is needed is a special electrode for

introduction into the bowel and an ordinary roller electrode. The rectal

electrode consists of a 6-inch wire bearing at one end a small metal

knob and fitted at the other into a metal cup which screws into the

handle of the electrode. The only part exposed is the metallic knob; the

rest is coated with some insulating material. The patient reclines on a

couch on his back, the rectal electrode is connected, and having been

vaselined is passed some three inches into the rectum. A current is

started with the secondary coil in such a position as to give only an

extremely weak current. The roller electrode is then wetted with hot

water and applied to the front of the abdomen. At first the patient

should feel nothing, but the current should slowly be increased until a

faint response is perceptible from the abdominal muscles. This gives the

required strength, and the roller electrode, pressed well into the

abdominal wall, should very slowly be moved along the course of the

large intestine beginning at the right iliac fossa. Thus a combination

of massage and faradic current is obtained, and the results are

particularly satisfactory. Treatment should be given on alternate days

immediately after breakfast, and should be persevered with for six or

eight weeks. The patient can be taught to administer it to himself.

_The Galvanic, Continuous or Direct Current._--In using the galvanic or

direct current the electrode must be covered with padded webbing or some

other absorbent material, the metal of the electrode never being allowed

to come in contact with the skin. The padding by retaining moisture

helps to make good contact, and also helps to guard against burning the

skin. But when a continuous current of 3 am. or more is passed for more

than 5 min. the electrodes must be raised periodically and the skin

inspected. If the current be too strong or applied for too long a time,

small blisters are raised which break and are very troublesome to heal.

Nor does the patient always feel much pain when this occurs. Also the

electrodes must be remoistened every five or six minutes, as they soon

become dry, and the skin will then be burnt. It is best to use a

solution of sodium bicarbonate. Again, the danger of burning the skin

depends on the density of the current per sq. in. of electrode, so that

a strong current through a small electrode will burn the skin, whereas

the same current through a larger electrode will produce a beneficial

effect. If the patient be immersed up to his neck in an electric bath,

much stronger currents can be passed without causing either pain or

injury, as in this case the whole area of the skin in contact with the

water acts as an electrode. In passing the current it must be remembered

that the negative electrode or kathode is the more painful of the two,

and its action more stimulating than the positive electrode or anode,

which is sedative. If a muscle be stimulated over its motor point, it

will contract with a sharp twitch and then become quiescent. With normal

muscle the KCC (kathodal closure contraction) is stronger than that

produced by the closure of the current at the anode ACC (anodal closure

contraction). And if the muscle be normal the opening contraction KOC

and AOC are not seen. When a galvanic current is passed along a nerve

its excitability is increased at the kathode and diminished at the

anode. The increased excitability at the kathode is katelectrotonus, and

the lowered excitability at the anode anelectrotonus. But since in a

patient the electrode cannot be applied directly to the nerve, the lines

of force from the electrode pass into the nerve both in an upward and

downward direction, and hence there are two poles produced by each

electrode. If the current be suddenly reversed, so that what was the

anode becomes the kathode, a stronger contraction is obtained than by

simply making and breaking the current. To avoid the four poles on the

nerve to be tested, it is found most satisfactory to have one electrode

placed at some distance, on the back or chest, not on the same limb.

As explained above, when the nerve supplying a muscle is diseased it no

longer responds to the faradic current. On further testing this with the

galvanic or continuous current it responds, but the contraction is not

brisk but begins slowly and relaxes slowly, though the contraction as a

whole may be larger than that of a normal muscle. This excessive

contraction is known as hyperexcitability to galvanism. This form of

contraction is that obtained when the muscle fibre itself is stimulated.

Again, whereas in normal muscle KCC > ACC, when the nerve is degenerated

KCC = ACC or ACC > KCC. Also in the more severe forms of nerve injury

tetanic contractions may be set up in the paralysed muscles, by closure

of the current either at the anode or kathode. These charges are known

as the reaction of degeneration or RD, and are of great value in

diagnosis. They occur only after sudden or acute damage to the nerve

cells of the anterior horn of the spinal cord, or to the motor nerve

fibres proceeding from these cells. Thus RD is present in infantile

paralysis, acute neuritis, &c., but absent in progressive muscular

atrophy where the wasting of nerve and muscle takes place extremely

slowly. The reaction of degeneration in the nerve is shown by

disappearance of reaction to either kind of current, preceded for some

days by hyperexcitability to either current. Where the muscle wasting is

due to a lesion in the muscle alone, as in ischaemic myositis (usually

due to injury from tight bandaging or badly applied splints), no

reaction of degeneration is found; the only change is a loss of power in

the contraction. If the damage to the anterior horn cells be only very

slight, there may only be partial RD, and the prognosis is given

according to the extent of RD. From this account it is clear that the

greatest value of the continuous current lies in its use in diagnosis.

But it is also applied extremely successfully, in combination with

massage, to cases of infantile paralysis. Wrist drop from lead poisoning

and lead neuritis of all kinds, reflex muscular atrophy and the muscular

wasting of hemiplegia, are all benefited by the continuous current; the

severe pain of sciatica, and the inflammation of the nerve sheath in

these cases, can be arrested more quickly by galvanic treatment than in

any other way. Nearly all forms of neuritis, both of the cranial and

other nerves, are best treated by the continuous current. The action in

all cases is to stimulate the natural tendency to repair, very largely

by improving the circulation through the injured parts.

Another effect of an electric current is electrolysis, and the phenomena

of electrolytic conduction involve not merely the ionization of the

compounds, but also the setting in motion of the ions towards their

respective poles. Solutions which conduct electric currents are called

electrolytes, and in the case of the human body the electrolyte is the

whole mass of the saline constituents in solution throughout the body.

When a current is passed through an electrolyte, dissociation into ions

takes place, the ions which are freed round the anode being called

anions and those which are freed round the kathode being called kations.

The anions carry negative charges and are consequently attracted by the

positive electricity of the anode. The kations carry positive charges,

hence they are repelled by the anode and attracted by the kathode. But a

certain number of molecules do not dissociate, and hence in an

electrolytic solution there are neutral molecules, anions and kations.

The chemical actions, and thus the antiseptic, remedial or toxic effects

of electrolytes, are due to the actions of their ions. The phosphides

and phosphates may be taken as examples. Some are extremely toxic, while

others are quite harmless. But it is to the phosphorus ion that the

toxic or therapeutic effect is due. In the phosphates the phosphorus is

part of a complex ion possessing quite different properties to those of

the phosphorus ion of the phosphides. The strikingly different effects

of the sulphates and sulphides are due to similar conditions, as also of

many other compounds. There are certain solvents, as alcohol,

chloroform, glycerin and vaseline which do not dissociate electrolytes,

and consequently the latter become inert when mixed with these solvents.

These solutions do not conduct electricity, and hence ionic effects are

extremely slow. A vaseline ointment containing 5% of phenol makes a good

dressing for an ulcer of the leg, and produces no irritant effect, but a

5% aqueous solution may be both caustic and toxic. Since the toxic or

therapeutic action of a solution is due to its ions, the action must be

proportional to the number of ions in a given volume, that is, the

action of an electrolyte depends on the degree of dissociation. Thus a

strong acid is one that is much dissociated, a weak acid one that has

undergone but little dissociation and so on. In 1896-1897 it was shown

that the bactericidal action of salts varies with their degree of

dissociation and therefore depends on the concentration of the active

ions. In the medical application of these facts it must be remembered

that when an ion is introduced into the body by electrolysis, it is

probably forced into the actual cellular constituents of the body,

whereas the drug administered by one of the usual methods though

circulating in the blood may perhaps never gain access to the cell

itself. Hence the different effects that have been recorded between a

drug administered by the mouth or subcutaneously and the same

administered by electrolysis. Thus a solution of cocaine injected

subcutaneously produces quite different effects to that introduced by

electrolysis. By the latter method it produces anaesthesia but does not

diffuse, and the anaesthesia remains strictly limited to the surface

covered by the electrode. It would appear that the ion is never

introduced into the general circulation but into the cell plasma.

In the technical working of medical electrolysis the most minute

precautions are required. The solution of the drug must be made with as

pure water as possible, recently distilled. The spongy substance forming

the electrode must be free from any trace of electrolytic substances.

Hence all materials used must be washed in distilled water. Absorbent

cotton answers all requirements and is easily procured. The area of

introduction can be exactly circumscribed by cutting a hole in a sheet

of adhesive plaster which is applied to the skin and on which the

electrolytic electrodes are pressed. The great advantage of electrolytic

methods is that it enables general treatment to be replaced by a

strictly local treatment, and the cells can be saturated exactly to the

degree and depth required. Strong antiseptics and materials that

coagulate albumen cannot be introduced locally by ordinary methods, as

the skin is impermeable to them, but by electrolysis they can be

introduced to the exact depth required. The local effects of the ions

depend on the dosage; thus a feeble dose of the ions of zinc stimulates

the growth of hair, but a stronger dose produces the death of the

tissue. Naturally the different ions produce different effects. Thus the

ions of the alkalis and magnesium are caustic, those of the alkaline

earthy metals produce actual mortification of the tissue and so on.

According to the ion chosen the effect may be caustic in various

degrees, antiseptic, coagulating, producing vascular or nervous changes,

&c., &c. And again electrolysis can also be used for extracting from the

body such ions as are injurious, as uric and oxalic acid from a patient

suffering from gout.

One of the latest advances is the treatment of ankylosed joints by the

electrolytic method, the electrolyte used being chloride of sodium, and

the marvellous results being attributed to the introduction of the

chlorine ions. This sclerolytic property of the current is applicable to

all parts of the body accessible to the current. Old cases of rheumatic

scleritis, entirely unaffected by the routine treatment of salicylates

and iodide, have often cleared up entirely under electrolytic treatment.

Cases of chronic iritis with adhesions and old pleural adhesions are

also suited for this method of procedure. Certain menstrual troubles of

women and also endometritis yield rapidly to electrolysis with a zinc

anode. Before this method of introduction, the zinc salts, though

excellent disinfectants, acted only on the surface in consequence of

their coagulating action on the albuminoids, but by the electric

current, under the influence of a difference of potential, the zinc iron

will penetrate to any desired depth. Cases of rodent ulcer unaffected by

all other methods of treatment have been cured by electric kataphoresis

with zinc ions, and the method is now being applied to the treatment of

inoperable malignant tumours. As very strong currents are required for

this latter, the patient has first to be anaesthetized by a general

anaesthetic. Another direction in which electric ions are being used is

that of the induction of local anaesthesia before minor surgical

operations. Cocaine is the drug used, the resulting anaesthesia is

absolute, and the operation can be made almost bloodless by the

admixture of suprarenal extract.

ELECTROTYPING, an application of the art of electroplating (q.v.) to

typography (q.v.). In copying engraved plates for printing purposes,

copper may be deposited upon the original plate, the surface of which is

first rendered slightly dirty, by means of a weak solution of wax in

turpentine or otherwise, to prevent adhesion. The reversed plate thus

produced is then stripped from the first and used as cathode in its

turn, with the result that even the finest lines of the original are

faithfully reproduced. The electrolyte commonly contains about 1-1/2 lb.

of copper sulphate and 1/2 lb. of strong sulphuric acid per gallon, and

is worked with a current density of about 10 amperes per sq. ft., which

should give a thickness of 0.000563 in. of copper per hour. As time is

an object, the conditions alluded to in the article on COPPER as being

favourable to the use of high current densities should be studied,

bearing in mind that a tough copper deposit of high quality is

essential. Moulds for reproducing plates or art-work are often taken in

plaster, beeswax mixed with Venice turpentine, fusible metal, or

gutta-percha, and the surface being rendered conductive by powdered

black-lead, copper is deposited upon it evenly throughout. For statuary,

and "undercut" work generally, an elastic mould--of glue and treacle

(80:20 parts)--may be used; the mould, when set, is waterproofed by

immersion in a solution of potassium bichromate followed by exposure to

sunlight, or in some other way. The best results, however, are obtained

by taking a wax cast from the elastic mould, and then from this a

plaster mould, which may be waterproofed with wax, black-leaded, and

used as cathode. In art-work of this nature the principal points to be

looked to in depositing are the electrical connexions to the cathode,

the shape of the anode (to secure uniformity of deposition), the

circulation of the electrolyte, and, in some cases, the means for escape

of anode oxygen. Silver electrotyping is occasionally resorted to for

special purposes.

ELECTRUM, ELECTRON (Gr. _[Greek: elektron]_, amber), an alloy of gold

and silver in use among the ancients, described by Pliny as containing

one part of silver to four of gold. The term is also applied in

mineralogy to native argentiferous gold containing from 20 to 50% of

silver. In both cases the name is derived from the pale yellow colour of

electrum, resembling that of amber.

ELEGIT (Lat. for "he has chosen"), in English law, a judicial writ of

execution, given by the Statute of Westminster II. (1285), and so called

from the words of the writ, that the plaintiff has chosen (_elegit_)

this mode of satisfaction. Previously to the Statute of Westminster II.,

a judgment creditor could only have the profits of lands of a debtor in

satisfaction of his judgment, but not the possession of the lands

themselves. But this statute provided that henceforth it should be _in

the election_ of the party having recovered judgment to have a writ of

_fieri facias_ (q.v.) unto the sheriff on lands and goods or else all

the chattels of the debtor and the one half of his lands until the

judgment be satisfied. Since the Bankruptcy Act 1883 the writ of

_elegit_ has extended to lands and hereditaments only. (See further

EXECUTION.)

ELEGY, a short poem of lamentation or regret, called forth by the

decease of a beloved or revered person, or by a general sense of the

pathos of mortality. The Greek word _[Greek: elegeia]_ is of doubtful

signification; it is usually interpreted as meaning a mournful or

funeral song. But there seems to be no proof that this idea of regret

for death entered into the original meaning of _[Greek: elegeia]_. The

earliest Greek elegies which have come down to us are not funereal,

although it is possible that the primitive _[Greek: elegeia]_ may have

been a set of words liturgically used, with music, at a burial. When the

elegy appears in surviving Greek literature, we find it dedicated, not

to death, but to war and love. Callinus of Ephesus, who flourished in

the 7th century, is the earliest elegist of whom we possess fragments. A

little later Tyrtaeus was composing his famous elegies in Sparta. Both

of these writers were, so far as we know, exclusively warlike and

patriotic. On the other hand, the passion of love inspires Mimnermus,

whose elegies are the prototypes not only of the later Greek pieces, and

of the Latin poems of the school of Tibullus and Propertius, but of a

great deal of the formal erotic poetry of modern Europe. In the 6th

century B.C., the elegies of Solon were admired; they are mainly lost.

But we possess more of the work of Theognis of Megara than of any other

archaic elegist, and in it we can observe the characteristics of Greek

elegy best. Here the Dorian spirit of chivalry reaches its highest

expression, and war is combined with manly love.

The elegy, in its calm movement, seems to have begun to lose currency

when the ecstasy of emotion was more successfully interpreted by the

various rhythmic and dithyrambic inventions of the Aeolic lyrists. The

elegy, however, rose again to the highest level of merit in Alexandrian

times. It was reintroduced by Philetas in the 3rd cent. B.C., and was

carried to extreme perfection by Callimachus. Other later Greek elegists

of high reputation were Asclepiades and Euphorion. But it is curious to

notice that all the elegies of these poets were of an amatory nature,

and that antiquity styled the funeral dirges of Theocritus, Bion and

Moschus--which are to us the types of elegy--not elegies at all, but

idylls. When the poets of Rome began their imitative study of

Alexandrian models, it was natural that the elegies of writers such as

Callimachus should tempt them to immediate imitation. Gallus, whose

works are unhappily lost, is known to have produced a great sensation in

Rome by publishing his translation of the poems of Euphorion; and he

passed on to the composition of erotic elegies of his own, which were

the earliest in the Latin language. If we possessed his once-famous

_Cytheris_, we should be able to decide the question of how much

Propertius, who is now the leading figure among Roman elegists, owed to

the example of Gallus. His brilliantly emotional _Cynthia_, with its

rich and unexampled employment of that alternation of hexameter and

pentameter which had now come to be known as the elegiac measure, seems,

however, to have settled the type of Latin elegy. Tibullus is always

named in conjunction with Propertius, who was his contemporary, although

in their style they were violently contrasted. The sweetness of Tibullus

was the object of admiration and constant imitation by the Latin poets

of the Renaissance, although Propertius has more austerely pleased a

later taste. Finally, Ovid wrote elegies of great variety in subject,

but all in the same form, and his dexterous easy metre closed the

tradition of elegiac poetry among the ancients. What remains in the

decline of Latin literature is all founded on a study of those masters

of the Golden Age.

When the Renaissance found its way to England, the word "elegy" was

introduced by readers of Ovid and Propertius. But from the beginning of

the 16th century, it was used in English, as it has been ever since, to

describe a funeral song or lament. One of the earliest poems in English

which bears the title of elegy is _The Complaint of Philomene_, which

George Gascoigne began in 1562, and printed in 1576. The _Daphnaida_ of

Spenser (1591) is an elegy in the strict modern sense, namely a poem of

regret pronounced at the obsequies of a particular person. In 1579

Puttenham had defined an elegy as being a song "of long lamentation."

With the opening of the 17th century the composition of elegies became

universal on every occasion of public or private grief. Dr Johnson's

definition, "_Elegy_, a short poem without points or turns," is

singularly inept and careless. By that time (1755) English literature

had produced many great elegies, of which the _Lycidas_ of Milton is by

far the most illustrious. But even Cowley's on Crashaw, Tickell's on

Addison, Pope's on an Unfortunate Lady, those of Quarles, and Dryden,

and Donne, should have warned Johnson of his mistake. Since the 18th

century the most illustrious examples of elegy in English literature

have been the _Adonais_ of Shelley (on Keats), the _Thyrsis_ of Matthew

Arnold (on Clough), and the _Ave atque Vale_ of Mr Swinburne (on

Baudelaire). It remains for us to mention what is the most celebrated

elegy in English, that written by Gray in a Country Churchyard. This,

however, belongs to a class apart, as it is not addressed to the memory

of any particular person. A writer of small merit, James Hammond

(1716-1742), enjoyed a certain success with his _Love Elegies_ in which

he endeavoured to introduce the erotic elegy as it was written by Ovid

and Tibullus. This experiment took no hold of English literature, but

was welcomed in France in the amatory works of Parny (1753-1814), in

those of Chenedolle (1769-1833), and of Millevoye (1782-1816). The

melancholy and sentimental elegies of the last named are the typical

examples of this class of poetry in French literature. Lamartine must be

included among the elegists, and his famous "Le Lac" is as eminent an

elegy in French as Gray's "Country Churchyard" is in English. The elegy

has flourished in Portugal, partly because it was cultivated with great

success by Camoens, the most illustrious of the Portuguese poets. In

Italian, Chiabrera and Filicaia are named among the leading national

elegists. In German literature, the notion of elegy as a poem of

lamentation does not exist. The famous Roman Elegies of Goethe imitate

in form and theme those of Ovid; they are not even plaintive in

character.

ELEGIAC VERSE has commonly been adopted by German poets for their

elegies, but by English poets never. Schiller defines this kind of

verse, which consists of a distich of which the first line is a

hexameter and the second a pentameter, in the following pretty

illustration:--

"In the hexameter rises the fountain's silvery column.

In the pentameter aye falling in melody back."

The word "elegy," in English, is one which is frequently used very

incorrectly; it should be remembered that it must be mournful,

meditative and short without being ejaculatory. Thus Tennyson's _In

Memoriam_ is excluded by its length; it may at best be treated as a

collection of elegies. Wordsworth's _Lucy_, on the other hand, is a

dirge; this is too brief a burst of emotion to be styled an elegy.

_Lycidas_ and _Adonais_ remain the two unapproachable types of what a

personal elegy ought to be in English. (E. G.)

ELEMENT (Lat. _elementum_), an ultimate component of anything, hence a

fundamental principle. _Elementum_ was used in Latin to translate the

Greek _[Greek: stoicheion]_ (that which stands in a _[Greek: stoichos]_,

or row), and is a word of obscure origin and etymology. The root of Lat.

_alere_, to nourish, has been suggested, thus making it a doublet of

_alimentum_, that which supports life; another explanation is that the

word represents LMN., the first three letters of the second part of the

alphabet, a parallel use to that of ABC. Apart from its application in

chemistry, which is treated below, the word is used of the rudiments or

_principia_ of any science or subject, as in Euclid's _Elements of

Geometry_, or in the "beggarly elements" (_[Greek: taptocha stoicheia]_,

of St Paul in Gal. iv. 9); in mathematics, of a fundamental concept

involved in an investigation, as the "elements" of a determinant; and in

electricity, of a galvanic (or voltaic) "element" in an electric cell

(see BATTERY: _Electric_). In astronomy, "element" is used of any one of

the numerical or geometrical data by which the course of a varying

phenomenon is computed; it is applied especially to orbital motion and

eclipses. The "elements of an orbit" are the six data by which the

position of a moving body in its orbit at any time may be determined.

The "elements of an eclipse" express and determine the motion of the

centre of the shadow-axis, and are the data necessary to compute the

phenomena of an eclipse during its whole course, as seen at any place.

In architecture the term "element" is applied to the outline of the

design of a Decorated window, on which the centres for the tracery are

found. These centres will all be found to fall on points which, in some

way or other, will be equimultiples of parts of the openings.

_Chemical Elements_.

Ancient ideas.

Like all other scientific concepts, that of an element has changed its

meaning many times in many ways during the development of science. Owing

to their very small amount of real chemical knowledge, the

generalizations of the ancients were necessarily rather superficial, and

could not stand in the face of the increasing development of practical

chemistry. Nevertheless we find the concept of an element as "a

substance from which all bodies are made or derived" held at the very

beginning of occidental philosophy. Thales regarded "water" as the

element of all things; his followers accepted his idea of a primordial

substance as the basis of all bodies, but they endeavoured to determine

some other general element or elements, like "fire" or "spirit," or

"love" and "hatred," or "fire," "water," "air" and "earth." We find in

this development an exact parallelism to the manner in which scientific

ideas generally arise, develop and change. They are created to point out

the common part in a variety of observed phenomena, in order to get some

leading light in the chaos of events. At first almost any idea will do,

if only it promises some comprehensive arrangement of the facts;

afterwards, the inconsistencies of the first trial make themselves felt;

the first idea is then changed to meet better the new requirements. For

a shorter or longer time the facts and ideas may remain in accord, but

the uninterrupted increase of empirical knowledge involves sooner or

later new fundamental alterations of the general idea, and in this way

there is a never-ceasing process of adaptation of the ideas to the

facts. As facts are unchangeable by themselves, the adaptation can be

only one-sided; the ideas are compelled to change according to the

facts. We must therefore educate ourselves to regard the ideas or

theories as the changing part of science, and keep ourselves ready to

accept even the most fundamental revision of current theories.

The first step in the development of the idea of elements was to

recognize that a _single_ principle would not prove sufficient to cover

the manifoldness of facts. Empedocles therefore conceived a double or

binary elementary principle; and Aristotle developed this idea a stage

further, stating two sets of binary antagonistic principles, namely

"dry-wet" and "hot-cold." The Aristotelian or peripatetic elements,

which played such a great role in the whole medieval philosophy, are the

representatives of the several binary combinations of these fundamental

properties, "fire" being hot and dry, "air" hot and wet, "water" cold

and wet, "earth" cold and dry. According to the amount of these

properties found in any body, these elements were regarded as having

taken part in forming this body. Concerning the reason why only these

properties were regarded as fundamental, we know nothing. They seem to

be taken at random rather than carefully selected; they relate only to

the sense of touch, and not to vision or any other sense, possibly

because deceptions in the sense of touch were regarded as non-existent,

while the other senses were apparently not so trustworthy. At any rate,

the Aristotelian elements soon proved to be rather inadequate to meet

the requirements of the increasing chemical knowledge; other properties

had therefore to be selected to represent the general behaviour of

chemical substances, and in this case we find them already much more

"chemical" in the modern sense.

Elements of the alchemists.

Among the various substances recognized by the chemists, certain classes

or groups readily distinguished themselves. First the metals, by their

lustre, their heaviness, and a number of other common properties.

According to the general principle of selecting a single substance as a

representative of the group, the metallic properties were represented by

"mercury." The theoreticians of the middle ages were rather careful to

point out that common mercury (the liquid metal of to-day) was not at

all to be identified with "philosophical" mercury, the last being simply

the _principle_ of metallic behaviour. In the same way combustibility

was represented by "sulphur," solubility by "salt," and occasionally the

chemically indifferent or refractory character by "earth." According to

the subsistence and preponderance of these properties in different

bodies, these were regarded as containing the corresponding elements;

conversely, just as experience teaches the chemist every day that by

proper treatment the properties of given bodies may be changed in the

most various ways, the observed changes of properties were ascribed to

the gain or loss of the corresponding elements. According to this

theory, which accounted rather well for a large number of facts, there

was no fundamental objection against trying to endow base metals with

the properties of the precious ones; to make artificial gold was a task

quite similar to the modern problem of, e.g. making artificial quinine.

The realization that there is a certain natural law preventing such

changes is of much later date. It is therefore quite unjust to consider

the work of the alchemists, who tried to make artificial gold, as

consummate nonsense. _A priori_ there was no reason why a change from

lead to gold should be less possible than a change from iron to rust;

indeed there is no _a priori_ reason against it now. But experience has

taught us that lead and gold are chemical elements in the modern sense,

and that there is a general experimental law that elements are not

transformable one into another. So experience taught the alchemists

irresistibly that in spite of the manifoldness of chemical changes it is

not always possible to change any given substance into another; the

possibilities are much more limited, and there is only a certain range

of substances to be obtained from a given one. The impossibility of

transforming lead or copper into noble metals proved to be only one case

out of many, and it was recognized generally that there are certain

chemical families whose members are related to one another by their

mutual transformability, while it is impossible to bridge the boundaries

separating these families.

Work of Robert Boyle.

The man who brought all these experiences and considerations into

scientific form was Robert Boyle. He stated as a general principle, that

only tangible and ponderable substances should be recognized as

elements, an element being a substance from which other substances may

be made, but which cannot be separated into different substances. He

showed that neither the peripatetic nor the alchemistic elements

satisfied this definition. But he was more of a critical than of a

synthetical turn of mind; although he established the correct

principles, he hesitated to point out what substances, among those known

at his time, were to be considered as elements. He only paved the way to

the goal by laying the foundations of analytical chemistry, i.e. by

teaching how to characterize and to distinguish different chemical

individuals. Further, by adopting and developing the corpuscular

hypothesis of the constitution of the ponderable substances, he

foreshadowed, in a way, the law of the conservation of the elements,

viz. that no element can be changed into another element; and he

considered the compound substances to be made up from small particles or

corpuscles of their elements, the latter retaining their essence in all

combinations. This hypothesis accounts for the fact that only a limited

number of other substances can be made from a given one--namely, only

those which contain the elements present in the given substance. But it

is characteristic of Boyle's critical mind that he did not shut his eyes

against a serious objection to his hypothesis. If the compound substance

is made up of parts of the elements, one would expect that the

properties of the compound substance would prove to be the sum of the

properties of the elements. But this is not the case, and chemical

compounds show properties which generally differ very considerably from

those of the compounds. On the one hand, the corpuscular hypothesis of

Boyle was developed into the atomic hypothesis of Dalton, which was

considered at the beginning of the 19th century as the very best

representation of chemical facts, while, on the other hand, the

difficulty as to the properties of the compounds remained the same as

Boyle found it, and has not yet been removed by an appropriate

development of the atomic hypothesis. Thus Boyle considered, e.g. the

metals as elements. However, it is interesting to note that he

considered the mutual transformation of the metals as not altogether

impossible, and he even tells of a case when gold was transformed into

base metal. It is a common psychological fact that a reformer does not

generally succeed in being wholly consistent in his reforming ideas;

there remains invariably some point where he commits exactly the same

fault which he set out to abolish. We shall find the same inconsistency

also among other chemical reformers. Even earlier than Boyle, Joachim

Jung (1587-1657) of Hamburg developed similar ideas. But as he did not

distinguish himself, as Boyle did, by experimental work in science, his

views exerted only a limited influence amongst his pupils.

Phlogiston theory.

In the times following Boyle's work we find no remarkable outside

development of the theory of elements, but a very important inside one.

Analytical chemistry, or the art of distinguishing different chemical

substances, was rapidly developing, and the necessary foundation for

such a theory was thus laid. We find the discussions about the true

elements disappearing from the text-books, or removed to an

insignificant corner, while the description of observed chemical changes

of different ways of preparing the same substance, as identified by the

same properties, and of the methods for recognizing and distinguishing

the various substances, take their place. The similarity of certain

groups of chemical changes, as, for example, combustion, and the inverse

process, reduction, was observed, and thus led to an attempt to shape

these most general facts into a common theory. In this way the theory of

"phlogiston" was developed by G.E. Stahl, phlogiston being (according to

the usual way of regarding general properties as being due to a

principle or element) the "principle of combustibility," similar to the

"sulphur" of the alchemists. This again must be regarded as quite a

legitimate step justified by the knowledge of the time. For experience

taught that combustibility could be _transferred_ by chemical action,

e.g. from charcoal to litharge, the latter being changed thereby into

combustible metallic lead; and according to Boyle's principle, that only

_bodies_ should be recognized as chemical elements, phlogiston was

considered as a body. From the fact that all leading chemists in the

second half of the 18th century used the phlogiston theory and were not

hindered by it in making their great discoveries, it is evident that a

sufficient amount of truth and usefulness was embodied in this theory.

It states indeed quite correctly the mutual relations between oxidation

and reduction, as we now call these very general processes, and was

erroneous only in regard to one question, which at that time had not

aroused much interest, the question of the change of weight during

chemical processes.

Lavoisier's reform.

It was only after Isaac Newton's discovery of universal gravitation that

weight was considered as a property of paramount interest and

importance, and that the question of the changes of weight in chemical

reactions became one worth asking. When in due time this question was

raised, the fact became evident at once, that combustion means not loss

but gain of weight. To be sure of this, it was necessary to know first

the chemical and physical properties of gases, and it was just at the

same time that this knowledge was developed by Priestley, Scheele and

others. Lavoisier was the originator and expounder of the necessary

reform. Oxygen was just discovered at that time, and Lavoisier gathered

evidence from all sides that the theory of phlogiston had to be turned

inside out to fit the new facts.

He realized that the sum total of the weights of all substances

concerned within a chemical change is not altered by the change. This

principle of the "conservation of weight" led at once to a simple and

unmistakable definition of a chemical element. As the weight of a

compound substance is the sum of the weights of its elements, the

compound necessarily weighs more than any of its elements. An element is

therefore a substance which, by being changed into another substance,

invariably increases its weight, and never gives rise to substances of

less weight. By the help of this criterion Lavoisier composed the first

table of chemical elements similar to our modern ones. According to the

knowledge of his time he regarded the alkalis as elements, although he

remarked that they are rather similar to certain oxides, and therefore

may possibly contain oxygen; the truth of this was proved at a later

date by Humphry Davy. But the inconsistency of the reformer, already

referred to, may be observed with Lavoisier. He included "heat and

light" in his list of elements, although he knew that neither of them

had weight, and that neither fitted his definition of an element; this

atavistic survival was subsequently removed from the table of the

elements by Berzelius in the beginning of the 19th century. In this way

the question of what substances are to be regarded as chemical elements

had been settled satisfactorily in a qualitative way, but it is

interesting to realize that the last step in this development, the

theory of Lavoisier, was based on quantitative considerations. Such

considerations became of paramount interest at once, and led to the

concept of the _combining weights of the elements_.

J.B. Richter's work.

The first discoveries in this field were made in the last quarter of the

18th century by J.B. Richter. The point at issue was a rather

commonplace one: it was the fact that when two neutral salt solutions

were mixed to undergo mutual chemical decomposition and recombination,

the resulting liquid was neutral again, i.e. it did not contain any

excess of acid or base. In other words, if two salts, A'B' and A" B",

composed of the acids A' and A" and the bases B' and B", undergo mutual

decomposition, the amount of the base B' left by the first salt, when

its acid A' united with the base B" to form a new salt A'B", was just

enough to make a neutral salt A"B' with the acid A" left by the second

salt. At first sight this looks quite simple and self-evident,--that

neutral salts should form neutral ones again and not acid or basic

ones,--but if this fact is once stated very serious quantitative

inferences may be drawn from it, as Richter showed. For if the symbols

A', A", B', B" denote at the same time such quantities of the acids and

bases as form neutral salts, then if three of these quantities are

determined, the fourth may be calculated from the others. This follows

from the fact that by decomposing A'B' with just the proper amount of

the other salt to form A'B", the remaining quantities B' and A" exist in

exactly the ratio to form a neutral salt A" B'. It is possible,

therefore, to ascribe to each acid and base a certain relative weight or

"combining weight" by which they will combine one with the other to form

neutral salts. The same reasoning may be extended to any number of acids

and bases.

It is true that Richter did not find out by himself this simplest

statement of the law of neutrality which he discovered, but he expressed

the same consequence in a rather clumsy way by a table of the combining

weights of different bases related to the unit amount of a certain acid,

and doing the same thing for the unit weight of every other acid. Then

he observed that the numbers in these different tables are proportionate

one to another. The same holds good if the corresponding series of the

combining weights of acids for unit weights of different bases were

tabulated. It was only a little later that a Berlin physicist, G.E.

Fischer, united the whole system of Richter's numbers simply into a

double table of acids and bases, taking as unit an arbitrarily chosen

substance, namely sulphuric acid. The following table by Fischer is

therefore the first table of combining weights.

_Bases._ _Acids._

Alumina 525 | Fluoric 427

Magnesia 615 | Carbonic 577

Ammoniac 672 | Sebacic 706

Lime 793 | Muriatic (hydrochloric) 712

Soda 859 | Oxalic 755

Strontiane 1329 | Phosphoric 979

Potash 1605 | Formic 988

Baryte 2222 | Sulphuric 1000

| Succinic 1209

| Nitric 1405

| Acetic 1480

| Citric 1683

| Tartaric 1694

It is interesting again to notice how difficult it is for the discoverer

of a new truth to find out the most simple and complete statement of his

discovery. It looks as if the amount of work needed to get to the top of

a new idea is so great that not enough energy remains to clear the very

last few steps. It is noteworthy also to observe how difficult it was

for the chemists of that time to understand the bearing of Richter's

work. Although a summary of his results was published in Berthollet's

_Essai de statique chimique_, one of the most renowned chemical books of

that time, nobody dared for a long time to take up the scientific

treasure laid open for all the world.

John Dalton's atomic theory.

At the beginning of the 19th century the same question was taken up from

quite another standpoint. John Dalton, in his investigations of the

behaviour of gases, and in order to understand more easily what happened

when gases were absorbed by liquids, used the corpuscular hypothesis

already mentioned in connexion with Boyle. While he depicted to himself

how the corpuscles, or, as he preferred to call them, the "atoms" of

the gases, entered the interstices of the atoms of the liquids in which

they dissolved, he asked himself: Are the several atoms of the same

substance exactly alike, or are there differences as between the grains

of sand? Now experience teaches us that it is impossible to separate,

for example, a quantity of pure water into two samples of somewhat

different properties. When a pure substance is fractionated by partial

distillation or partial crystallization or partial change into another

substance by chemical means, we find constantly that the residue is not

changed in its properties, as it would be if the atoms were slightly

different, since in that case e.g. the lighter atoms would distil first

and leave behind the heavier ones, &c. Therefore we must conclude that

all atoms of the same kind are exactly alike in shape and weight. But,

if this be so, then all combinations between different atoms must

proceed in certain invariable ratios of the weights of the elements,

namely by the ratio of the weights of the atoms. Now it is impossible to

weigh the atoms directly; but if we determine the ratio of the weights

in which oxygen and hydrogen combine to form water, we determine in this

way also the relative weight of their atoms. By a proper number of

analyses of simple chemical compounds we may determine the ratios

between the weights of all elementary atoms, and, selecting one of them

as a standard or unit, we may express the weight of all other atoms in

terms of this unit. The following table is Dalton's (_Mem. of the Lit.

and Phil. Soc. of Manchester_ (II.), vol. i. p. 287, 1805).

_Table of the Relative Weights of the Ultimate Particles of Gaseous

and other Bodies._

Hydrogen 1 | Nitrous oxide 13.7

Azot 4.2 | Sulphur 14.4

Carbone 4.3 | Nitric acid 15.2

Ammonia 5.2 | Sulphuretted hydrogen 15.4

Oxygen 5.5 | Carbonic acid 15.3

Water 6.5 | Alcohol 15.1

Phosphorus 7.2 | Sulphureous acid 19.9

Phosphuretted hydrogen 8.2 | Sulphuric acid 25.4

Nitrous gas 9.3 | Carburetted hydrogen from

Ether 9.6 | stagnant water 6.3

Gaseous oxide of carbone 9.8 | Olefiant gas 5.3

Dalton at once drew a peculiar inference from this view. If two elements

combine in different ratios, one must conclude that different numbers of

atoms unite. There must be, therefore, a simple ratio between the

quantities of the one element united to the same quantity of the other.

Dalton showed at once that the analysis of carbon monoxide and of

carbonic acid satisfied this consequence, the quantity of oxygen in the

second compound being double the quantity in the first one. A similar

relation holds good between marsh gas and olefiant gas (ethylene). This

is the "law of multiple proportions" (see ATOM). By these considerations

Dalton extended the law of combining weights, which Richter had

demonstrated only for neutral salts, to all possible chemical compounds.

While the scope of the law was enormously extended, its experimental

foundation was even smaller than with Richter. Dalton did not concern

himself very much with the experimental verification of his ideas, and

the first communication of his theory in a paper on the absorption of

gases by liquids (1803) attracted as little notice as Richter's

discoveries. Even when T. Thomson published Dalton's views in an

appendix to his widely read text-book of chemistry, matters did not

change very much. It was only by the work of J.J. Berzelius that the

enormous importance of Dalton's views was brought to light.

Work of J.J. Berzelius.

Berzelius was at that time busy in developing a trustworthy system of

chemical analysis, and for this purpose he investigated the composition

of the most important salts. He then went over the work of Richter, and

realized that by his law he could check the results of his analyses. He

tried it and found the law to hold good in most cases; when it did not,

according to his analyses, he found that the error was on his own side

and that better analyses fitted Richter's law. Thus he was prepared to

understand the importance of Dalton's views and he proceeded at once to

test its exactness. The result was the best possible. The law of the

combining weights of the atoms, or of the atomic weights, proved to

hold good in every case in which it was tested. All chemical

combinations between the several elements are therefore regulated by

weight according to certain numbers, one for each element, and

combinations between the elements occur only in ratios given by these

weights or by simple multiples thereof. Consequently Berzelius regarded

Dalton's atomic hypothesis as proved by experiment, and became a strong

believer in it.

At the same time W.H. Wollaston had discovered independently the law of

multiple proportions in the case of neutral and acid salts. He gave up

further work when he learned of Dalton's ideas, but afterwards he

pointed out that it was necessary to distinguish the _hypothetical_ part

in Dalton's views from their _empirical_ part. The latter is the law of

combining weights, or the law that chemical combination occurs only

according to certain numbers characteristic for each element. Besides

this purely experimental law there is the hypothetical explanation by

the assumption of the existence of atoms. As it is not proved that this

explanation is the only one possible, the existence of the law is not a

proof of the existence of the atoms. He therefore preferred to call the

characteristic combining numbers of the elements not "atomic weights"

but "chemical equivalents."

Although there were at all times chemists who shared Wollaston's

cautious views, the atomic hypothesis found general acceptance because

of its ready adaptability to the most diverse chemical facts. In our

time it is even rather difficult to separate, as Wollaston did, the

empirical part from the hypothetical one, and the concept of the atom

penetrates the whole system of chemistry, especially organic chemistry.

If we compare the work of Dalton with that of Richter we find a

fundamental difference. Richter's inference as to the existence of

combining weights in salts is based solely on an experimental

observation, namely, the persistence of neutrality after double

decomposition; Dalton's theory, on the contrary, is based on the

hypothetical concept of the atom. Now, however favourably one may think

of the probability of the existence of atoms, this existence is really

not an observed fact, and it is necessary therefore to ask: Does there

exist some general fact which may lead directly to the inference of the

existence of combining weights of the elements, just as the persistence

of neutrality leads to the same consequence as to acids and bases? The

answer is in the affirmative, although it took a whole century before

this question was put and answered. In a series of rather difficult

papers (_Zeits. f. Phys. Chem._ since 1895, and _Annalen der

Naturphilosophie_ since 1902), Franz Wald (of Kladno, Bohemia) developed

his investigations as to the genesis of this general law. Later, W.

Ostwald (Faraday lecture, _Trans. Chem. Soc._, 1904) simplified Wald's

reasoning and made it more evident.

The general fact upon which the necessary existence of combining weights

of the elements may be based is the shifting character of the boundary

between elements and compounds. It has already been pointed out that

Lavoisier considered the alkalis and the alkaline earths as elements,

because in his time they had not been decomposed. As long as the

decomposition had not been effected, these compounds could be considered

and treated like elements without mistake, their combining weight being

the sum of the combining weights of their (subsequently discovered)

elements. This means that compounds enter in reaction with other

substances as a whole, just as elements do. In particular, if a compound

AB combines with another substance (elementary or compound) C to form a

ternary compound ABC, it enters this latter as a whole, leaving behind

no residue of A or B. Inversely, if a ternary compound ABC be changed

into a binary one AB by taking away the element C, there will not be

found any excess of A or B, but both elements will exhibit just the same

ratio in the binary as in the ternary compound.

Experimentally this important fact was proved first by Berzelius, who

showed that by oxidizing lead sulphide, PbS, to lead sulphate, PbSO4, no

excess either of sulphur or lead could be found after oxidation; the

same held good with barium sulphite, BaSO3, when converted into barium

sulphate, BaSO4. On a much larger scale and with very great accuracy

the inverse was proved half a century later by J.S. Stas, who reduced

silver chlorate, AgClO3, silver bromate, AgBrO3, and silver iodate,

AgIO3, to the corresponding binary compounds, AgCl, AgBr and AgI, and

searched in the residue of the reaction for any excess of silver or

halogen. As the tests for these substances are among the most sensitive

in analytical chemistry, the general law underwent a very severe test

indeed. But the result was the same as was found by Berzelius--no excess

of one of the elements could be discovered. We may infer, therefore,

generally that compounds enter ulterior combinations without change of

the ratio of their elements, or that the ratio between different

elements in their compounds is the same in binary and ternary (or still

more complicated) combinations.

This law involves the existence of general combining weights just in the

same way as the law of neutrality with double decomposition of salts

involves the law of the combining weights of acids and bases. For if the

ratio between A and B is determined, this same ratio must obtain in all

ternary and more complicated compounds, containing the same elements.

The same is true for any other elements, C, D, E, F, &c., as related to

A. But by applying the general law to the ternary compound ABC the same

conclusion may be drawn as to the ratio A : C in all compounds

containing A and C, or B : C in the corresponding compounds. By

reasoning further in the same way, we come to the conclusion that only

such compounds are possible which contain elements according to certain

ratio-numbers, i.e. their combining weight. Any other ratio would

violate the law of the integral reaction of compounds.

As to the law of multiple proportions, it may be deduced by a similar

reasoning by considering the possible combinations between a compound,

e.g. AB, and one of its elements, say B. AB and B can combine only

according to their combining weights, and therefore the quantity of B

combining with AB is equal to the quantity of AB which has combined with

A to form AB. The new combination is therefore to be expressed by AB2.

By extending this reasoning in the same way, we get the general

conclusion that any compounds must be composed according to the formula

A_m B_n C_p..., where m, n, p, &c., are integers.

The bearing of these considerations on the atomic hypothesis is not to

disprove it, but rather to show that the existence of the law of

combining weights, which has been considered for so long as a proof of

the truth of this hypothesis, does not necessarily involve such a

consequence. Whether atoms may prove to exist or not, the law of

combining weights is independent thereof.

Atomic weight determinations.

Two problems arose from the discoveries of Dalton and Berzelius. The

first was to determine as exactly as possible the correct numbers of the

combining weights. The other results from the fact that the same

elements may combine in different ratios. Which of these ratios gives

the true ratio of the atomic weights? And which is the multiple one?

Both questions have had most ample experimental investigation, and are

now answered rather satisfactorily. The first question was a purely

technical one; its answer depended upon analytical skill, and Berzelius

in his time easily took the lead, his numbers being readily accepted on

the continent of Europe. In England there was a certain hesitation at

first, owing to Prout's assumption (see below), but when Turner, at the

instigation of the British Association for the Advancement of Science,

tested Berzelius's numbers and found them entirely in accordance with

his own measurements, these numbers were universally accepted. But then

a rather large error in one of Berzelius's numbers (for carbon) was

discovered in 1841 by Dumas and Stas, and a kind of panic ensued. New

determinations of the atomic weights were undertaken from all sides. The

result was most satisfactory for Berzelius, for no other important error

was discovered, and even Dumas remarked that repeating a determination

by Berzelius only meant getting the same result, if one worked properly.

In later times more exact measurements, corresponding to the increasing

art in analysis, were carried out by various workers, amongst whom J.S.

Stas distinguished himself. But even the classical work of Stas proved

not to be entirely without error; for every period has its limit in

accuracy, which extends slowly as science extends. In recent times

American chemists have been especially prominent in work of this kind,

and the determinations of E.W. Morley, T.W. Richards and G.P. Baxter

rank among the first in this line of investigation.

During this work the question arose naturally: How far does the

_exactness_ of the law extend? It is well known that most natural laws

are only approximations, owing to disturbing causes. Are there

disturbing causes also with atomic weights? The answer is that as far as

we know there are none. The law is still an exact one. But we must keep

in mind that an absolute answer is never possible. Our exactness is in

every case limited, and as long as the possible variations lie behind

this limit, we cannot tell anything about them. In recent times H.

Landolt has doubted and experimentally investigated the law of the

conservation of weight.

Landolt's experiments were carried out in vessels of the shape of an

inverted U, each branch holding one of the substances to react one on

the other. Two vessels were prepared as equal as possible and hung on

both sides of a most sensitive balance. Then the difference of weight

was determined in the usual way by exchanging both the vessels on the

balance. After this set of weighings one of the vessels was inverted and

the chemical reaction between the contained substances was performed;

then the double weighing was repeated. Finally also the second vessel

was inverted and a third set of weighings taken. From blank experiments

where the vessels were filled with substances which did not react one on

the other, the maximum error was determined to 0.03 milligramme. The

reactions experimented with were: silver salts with ferrous sulphate;

iron on copper sulphate; gold chloride and ferrous chloride; iodic acid

and hydriodic acid; iodine and sodium sulphite; uranyl nitrate and

potassium hydrate; chloral hydrate and potassium hydrate; electrolysis

of cadmium iodide by an alternating current; solution of ammonium

chloride, potassium bromide and uranyl nitrate in water, and

precipitation of an aqueous solution of copper sulphate by alcohol. In

most of these experiments a slight diminution of weight was observed

which exceeded the limit of error distinctly in two cases, viz. silver

nitrate with ferrous sulphate and iodic acid with hydriodic acid, the

loss of weight amounting from 0.068 to 0.199 mg. with the first and

0.047 to 0.177 mg. with the second reaction on about 50 g. of substance.

As each of these reactions had been tried in nine independent

experiments, Landolt felt certain that there was no error of observation

involved. But when the vessels were covered inside with paraffin wax, no

appreciable diminution of weight was observed.

These experiments apparently suggested a small decrease of weight as a

consequence of chemical processes. On repeating them, however, and

making allowance for the different amounts of water absorbed on the

surface of the vessel at the beginning and end of the experiment,

Landolt found in 1908 (_Zeit. physik. Chem._ 64, p. 581) that the

variations in weight are equally positive and negative, and he concluded

that there was no change in weight, at least to the extent of 1 part in

10,000,000.

The periodic arrangement.

There is still another question regarding the numerical values of the

atomic weights, namely: Are there relations between the numbers

belonging to the several elements? Richter had arranged his combining

weights according to their magnitude, and endeavoured to prove that they

form a certain mathematical series. He also explained the incompleteness

of his series by assuming that certain acids or bases requisite to the

filling up of the gaps in the series, were not yet known. He even had

the satisfaction that in his time a new base was discovered, which

fitted rather well into one of his gaps; but when it turned out

afterwards that this new base was only calcium phosphate, this way of

reasoning fell into discredit and was resumed only at a much later date.

To obtain a correct table of atomic weights the second question already

mentioned, viz. how to select the correct value in the case of multiple

proportions, had to be answered. Berzelius was constantly on the

look-out for means to distinguish the true atomic weights from their

multiples or sub-multiples, but he could not find an unmistakable test.

The whole question fell into a terrible disorder, until in the middle of

the 19th century S. Cannizzaro showed that by taking together all

partial evidences one could get a system of atomic weights consistent in

itself and fitting the exigencies of chemical systematics. Then a

startling discovery was made by the same method which Richter had tried

in vain, by arranging all atomic weights in one series according to

their numerical values.

_The Periodic Law._--The history of this discovery is rather long. As

early as 1817 J.W. Dobereiner of Jena drew attention to the fact that

the combining weight of strontium lies midway between those of calcium

and barium, and some years later he showed that such "triads" occurred

in other cases too. L. Gmelin tried to apply this idea to all elements,

but he realized that in many cases more than three elements had to be

grouped together. While Ernst Lenssen applied the idea of triads to the

whole table of chemical elements, but without any important result, the

other idea of grouping more than three elements into series according to

their combining weights proved more successful. It was the concept of

homologous series just developed in organic chemistry which influenced

such considerations. First Max von Pettenkofer in 1850 and then J.B.A.

Dumas in 1851 undertook to show that such a series of similar elements

could be formed, having nearly constant differences between their

combining weights. It is true that this idea in all its simplicity did

not hold good extensively enough; so J.P. Cooke and Dumas tried more

complicated types of numerical series, but only with a temporary

success.

The idea of arranging all elements in a single series in the order of

the magnitude of their combining weights, the germ of which is to be

found already in J.B. Richter's work, appears first in 1860 in some

tables published by Lothar Meyer for his lectures. Independently, A.E.B.

de Chancourtois in 1862, J.A.R. Newlands in 1863, and D.I. Mendeleeff in

1869, developed the same idea with the same result, namely, that it is

possible to divide this series of all the elements into a certain number

of very similar parts. In their papers, which appeared in the same year,

1869, Lothar Meyer and Mendeleeff gave to all these trials the shape now

generally adopted. They succeeded in proving beyond all doubt that this

series was of a _periodic character_, and could be cut into shorter

pieces of similar construction. Here again gaps were present to be

filled up by elements to be discovered, and Mendeleeff, who did this,

predicted from the general regularity of his table the properties of

such unknown elements. In this case fate was more kind than with

Richter, and science had the satisfaction of seeing these predictions

turn out to be true.

The following table contains this periodic arrangement of the elements

according to their atomic weight. By cutting the whole series into

pieces of eight elements (or more in several cases) and arranging these

one below another in the alternating way shown in the table, one finds

similar elements placed in vertical series whose properties change

gradually and with some regularity according to their place in the

table. Not only the properties of the uncombined elements obey this

rule, but also almost all properties of similar compounds of the

elements.

+--------+-----------+----------+----------+----------+----------+----------+----------+----------------------------+

|He 4.0 |Li 7.03 |Be 9.1 |B 11.0 |C 12.00 |N 14.01 |O 16.00 |F 19.0 | .. .. .. |

| Ne 20 | Na 23.00 | Mg 24.32| Al 27.1 | Si 28.4 | P 31.0 | S 32.06 | Cl 35.45| .. .. .. |

|Ar 39.9 |K 39.15 |Ca 40.1 |Sc 44.1 |Ti 48.1 |V 51.2 |Cr 52.0 |Mn 55.0 |Fe 55.9, Ni 58.7, Co 59.0 |

| .. | Cu 63.6 | In 65.4 | Ga 70 | Ge 72.5 | As 75.0 | Se 79.2 | Br 79.96| .. .. .. |

|Kr 83.0 |Rb 85.5 |Sr 87.6 |Y 89.0 |Zr 90.6 |Cb(Nb) 94 |Mo 96.0 | .. |Ru 101.7, Rh 103.0, Pd 106.5|

| .. | Ag 107.93| Cd 112.4| In 115 | Sn 119.0| Sb 120.2| Te 127.6| I 126.97| .. .. .. |

|Xe 130.7|Cs 132.9 |Ba 137.4 |La 138.9 |Ce &c. 140|Ta 181 |W 184 | .. |Os 191, Ir 193.0, Pt 194.8 |

| .. | Au 197.2 | Hg 200.0| Tl 204.1| Pb 206.9| Bi 208.0| .. | .. | .. .. .. |

| .. | .. |Ra 225 | .. |Th 232.5 | .. |U 238.5 | .. | .. .. .. |

+--------+-----------+----------+----------+----------+----------+----------+----------+----------------------------+

But upon closer investigation it must be confessed that these

regularities can be called only rules, and not laws. In the first line

one would expect that the steps in the values of the atomic weights

should be regular, but it is not so. There are even cases when it is

necessary to invert the order of the atomic weights to satisfy the

chemical necessities. Thus argon has a larger number than potassium, but

must precede it to fit into its proper place. The same is true of

tellurium and iodine. It looks as if the real elements were scattered

somewhat haphazard on a regular table, or as if some independent factor

were active to disturb an existing regularity. It may be that the new

facts mentioned above will lead also to an explanation of these

irregularities; at present we must recognize them and not try to explain

them away. Such considerations have to be kept in mind especially in

regard to the very numerous attempts to express the series of combining

weights in a mathematical form. In several cases rather surprising

agreements were found, but never without exception. It looks as if some

very important factor regulating the whole matter is still unknown, and

before this has been elucidated no satisfactory treatment of the matter

is possible. It seems therefore premature to enter into the details of

these speculations.

Transmutation of elements.

In recent times not only our belief in the absolute exactness of the law

of the conservation of weight has been shaken, but also our belief in

the law of the conservation of the elements. The wonderful substance

radium, whose existence has made us to revise quite a number of old and

established views, seems to be a fulfilment of the old problem of the

alchemists. It is true that by its help lead is not changed into gold,

but radium not only changes itself into another element, helium

(Ramsay), but seems also to cause other elements to change. Work in this

line is of present day origin only and we do not know what new laws will

be found to regulate these most unexpected reactions (see

RADIOACTIVITY). But we realize once more that no law can be regarded as

free from criticism and limitation; in the whole realm of exact sciences

there is no such thing as the Absolute.

Prout's assumption.

Another question regarding the values of atomic weights was raised very

soon after their first establishment. From the somewhat inexact first

determinations William Prout concluded that all atomic weights are

multiples of the atomic weight of hydrogen, thus suggesting all other

elements to be probably made up from condensed hydrogen. Berzelius found

his determinations not at all in accordance with this assumption, and

strongly opposed the arbitrary rounding off of the numbers practised by

the partisans of Prout's hypothesis. His hypothesis remained alive,

although almost every chemist who did _exact_ atomic weight

determinations, especially Stas, contradicted it severely. Even in our

time it seems to have followers, who hope that in some way the existing

experimental differences may disappear. But one of the most important

and best-known relations, that between _hydrogen_ and _oxygen_, is

certainly different from the simple ratio 1 : 16, for it has been

determined by a large number of different investigators and by different

methods to be undoubtedly lower, namely, 1 : 15.87. Therefore, if

Prout's hypothesis contain an element of truth, by the act of

condensation of some simpler substance into the present chemical

elements a change of weight also must have occurred, such that the

weight of the element did not remain exactly the weight of the simpler

substance which changed into it. We have already remarked that such

phenomena are not yet known with certainty, but they cannot be regarded

as utterly impossible.

International table of atomic weights.

It may here be mentioned that the internationality of science has shown

itself active also in the question of atomic weights. These numbers

undergo incessantly small variations because of new work done for their

determination. To avoid the uncertainty arising from this inevitable

state of affairs, an international committee was formed by the

co-operation of the leading chemical societies all over the world, and

an international table of the most probable values is issued every year.

The following table is that for 1910:--

_International Atomic Weights_, 1910.

Atomic | Atomic

Weights. | Weights.

Name. Symbol. O = 16. | Name. Symbol. O = 16.

|

Aluminium Al 27.1 | Mercury Hg 200.0

Antimony Sb 120.2 | Molybdenum Mo 96.0

Argon Ar 39.9 | Neodymium Nd 144.3

Arsenic As 74.96 | Neon Ne 20.0

Barium Ba 137.37 | Nickel Ni 58.68

Beryllium Be \ 9.1 | Nitrogen N 14.01

(Glucinum) Gl / | Osmium Os 190.9

Bismuth Bi 208.0 | Oxygen O 16.00

Boron B 11.0 | Palladium Pd 106.7

Bromine Br 79.92 | Phosphorus P 31.0

Cadmium Cd 112.40 | Platinum Pt 195.0

Caesium Cs 132.81 | Potassium K 39.10

Calcium Ca 40.09 | Praseodymium Pr 140.6

Carbon C 12.00 | Radium Ra 226.4

Cerium Ce 140.25 | Rhodium Rh 102.9

Chlorine Cl 35.46 | Rubidium Rb 85.45

Chromium Cr 52.0 | Ruthenium Ru 101.7

Cobalt Co 58.97 | Samarium Sm 150.4

Columbium Cb \ 93.5 | Scandium Sc 44.1

(Niobium) (Nb) / | Selenium Se 79.2

Copper Cu 63.57 | Silicon Si 28.3

Dysprosium Dy 162.5 | Silver Ag 107.88

Erbium Er 167.4 | Sodium Na 23.00

Europium Eu 152.0 | Strontium Sr 87.62

Fluorine F 19.0 | Sulphur S 32.07

Gadolinium Gd 157.3 | Tantalum Ta 181.0

Gallium Ga 69.9 | Tellurium Te 127.5

Germanium Ge 72.5 | Terbium Th 159.2

Gold Au 197.2 | Thallium Tl 204.0

Helium He 4.0 | Thorium Th 232.42

Hydrogen H 1.008 | Thulium Tm 168.5

Indium In 114.8 | Tin Sn 119.0

Iodine I 126.92 | Titanium Ti 48.1

Iridium Ir 193.1 | Tungsten W 184.0

Iron Fe 55.85 | Uranium U 238.5

Krypton Kr 83.0 | Vanadium V 51.2

Lanthanum La 139.0 | Xenon Xe 130.7

Lead Pb 207.10 | Ytterbium

Lithium Li 7.00 | (Neoytterbium) Yb 172.0

Lutecium Lu 174.0 | Yttrium Y 89.0

Magnesium Mg 24.32 | Zinc Zn 65.37

Manganese Mn 54.93 | Zirconium Zr 90.6

Concluding remarks.

In the long and manifold development of the concept of the element one

idea has remained prominent from the very beginning down to our times:

it is the idea of a primordial matter. Since the naive statement of

Thales that all things came from water, chemists could never reconcile

themselves to the fact of the conservation of the elements. By an

experimental investigation which extended over five centuries and more,

the impossibility of transmuting one element into another--for example,

lead into gold--was demonstrated in the most extended way, and

nevertheless this law has so little entered the consciousness of the

chemists that it is seldom explicitly stated even in carefully written

text-books. On the other side the attempts to reduce the manifoldness of

the actual chemical elements to one single primordial matter have never

ceased, and the latest development of science seems to endorse such a

view. It is therefore necessary to consider this question from a most

general standpoint.

In physical science, the chemical elements may be compared with such

concepts as _mass_, _momentum_, _quantity of electricity_, _entropy_ and

such like. While mass and entropy are determined univocally by a unit

and a number, quantity of electricity has a unit, a number and a sign,

for it can be positive as well as negative. Momentum has a unit, a

number and a direction in space. Elements do not have a common unit as

the former magnitudes, but every element has its own unit, and there is

no transition from one to another. All these magnitudes underlie a law

of conservation, but to a very different degree. While mass was

considered as absolutely invariable in the classical mechanics, the

newer theories of the electrical constitution of matter make mass

dependent on the velocity of the moving electron. Momentum also is not

entirely conservative because it can be changed by light-pressure.

Entropy is known as constantly increasing, remaining constant only in an

ideal limiting case. With chemical elements we observe the same thing as

with momentum; though till recently considered as conservative, there is

now experimental evidence that they do not always show this character.

Generally the laws of the conservation of mass, weight and elements are

expressed as the "law of the conservation of matter." But this

expression lacks scientific exactness because the term "matter" is

generally not defined exactly, and because only the above-named

properties of ponderable objects do not change, while all other

properties do to a greater or less extent. Considered in the most

general way, we may define matter as a complex of gravitational, kinetic

and chemical energies, which are found to cling together in the same

space. Of these energies the capacity factors, namely, weight, mass and

elements, are conservative as described, while the intensity factors,

potential, velocity and affinity, may change in wide limits. To explain

why we find these energies constantly combined one with another, we only

have to think of a mass without gravity or a ponderable body without

mass. The first could not remain on earth because every movement would

carry it into infinite space, and the second would acquire infinite

velocity by the slightest push and would also disappear at once.

Therefore only such objects which have both mass and weight can be

handled and can be objects of our knowledge. In the same way all other

energies come to our knowledge only by being (at least temporarily)

associated with this combination of mass and weight. This is the true

meaning of the term "matter."

In this line of ideas matter appears not at all as a primary concept,

but as a complex one; there is therefore no reason to consider matter as

the last term of scientific analysis of chemical facts, and the idea of

a primordial matter appears as a survival from the very first beginning

of European natural philosophy. The most general concept science has

developed to express the variety of experience is _energy_, and in terms

of energy (combined with number, magnitudes, time and space) all

observed and observable experiences are to be described. (W. O.)