Highlanders of Scotland. Dirks are worn by midshipmen and cadets of the
Royal Navy, and still form part of the full Highland costume.
DIRK-HARTOG ISLAND, on the west coast of Australia, 45 miles long, north to
south, and 10 miles broad.
DIRT-BEDS, in geology, layers of ancient soil, such as those in the Oolitic
strata of the Isle of Purbeck (Dorset), which contain the stumps of trees
that once grew in them.
DISABILITY, in law, incapacity to do any legal act. It is either
_absolute_, which wholly disables the person, such as outlawry or
excommunication--or _partial_, such as infancy, coverture, insanity, or
drunkenness.
DISBARRING, or DISBARMENTS, expelling a barrister from the Bar, a
prerogative which, in England, is possessed by the benchers of each of the
four Inns of Court. The party disbarred may lodge an appeal with the judges
in their capacity of visitors.
DISC, or DISK, the central part of the capitulum of compositae, surrounded
by the ray. Also a part of a flower, sometimes cup-shaped, at the base of
the stamens, consisting in some cases of rudimentary stamens, in others of
the modified receptacle.--In astronomy the term is applied to the visible
face or figure exhibited by the sun, moon, or a planet. In the case of the
moon and certain planets it may be of gibbous, semicircular, or crescent
form.
[Illustration: Discharging Arch]
DISCHARGING ARCH, an arch formed in the substance of a wall to relieve the
part which is below it from the superincumbent weight. Such arches are
commonly used over lintels and flat-headed openings.
DISCIPLINE, BOOKS OF, two books connected with the Church of Scotland. The
_First Book of Discipline_ was drawn up by John Knox and four other
ministers, and laid before the General Assembly in 1560. Though not
formally ratified by the Privy Council, it was secretly subscribed by the
greater part of the nobility and barons who were members of the Council.
Another similar document, the _Second Book of Discipline_, was prepared and
sanctioned by the General Assembly of 1578, and has from that time been
recognized as the authorized standard of the Church of Scotland in respect
of government and discipline.
DISCLAIM'ER, in its stricter legal sense, a plea containing renunciation or
a denial of some claim alleged to have been made by the party pleading.
DISCOMYCETES, a large section of the ascomycetous Fungi, distinguished by
the fact that the hymenium covers the surface of an open, disc-like or
cup-shaped fruit-body called an _apothecium_. It includes many important
genera, such as Dasyscypha, Peziza, and Sclerotinia.
DISCOPHO'RA, (1) a sub-class of the Hydrozoa, comprising most of the
organisms known as sea-jellies, jelly-fishes, and sea-nettles; (2) leeches
(q.v.).
DIS'COUNT, the charge made by a banker for interest of money advanced by
him on a bill or other document not presently due. In advancing money on
such a security the banker deducts the charge for interest on his advance
from the total amount represented on the security, pays the difference,
which is called the _proceeds_ of the bill, to the person parting with it,
and collects the full amount to reimburse himself for outlay and interest
at maturity. Popularly the term _discount_ is applied to any deduction from
the full amount of an account made by the party to whom it is paid,
especially on prompt or early payment. When a bill which has been
_discounted_ is paid by the acceptor before it is due, the discount allowed
for prepayment is called _rebate_.
DISCOV'ERY, in law, the act of revealing or making known any matter by a
defendant in his answer to a bill in chancery. The word is also used in
reference to the disclosure by a bankrupt of his property for the benefit
of his creditors, and to the right of a party to a lawsuit to obtain from
his adversary, on oath, full disclosure of the facts within his knowledge,
and production of the documents in his possession, pertinent to the action.
DISCUS, DISC, or DISK, among the Greeks and Romans a quoit of stone or
metal, convex on both its sides, sometimes perforated in the middle. The
players aimed at no mark, but simply tried to throw the quoit to the
greatest possible distance. It was sometimes furnished with a thong of
leather to assist in the throwing. The thrower of the discus was called
_discobolus_.
DISEASE, any morbid state of the body, or of any organ or part of the body.
Diseases are described as local or constitutional, epidemic, endemic,
contagious, acute, and chronic. As to their classification, see _Nosology_.
The influence of the parents on the organization of the child is so great
that not only peculiarities of external form, but the peculiar
constitution, the greater or less activity and development of the organs,
are found to pass from parent to child. As it is in the particular state of
the several tissues and functions that certain diseases have their
foundation, the liability to such affections is inherited with the organic
structure, and children are not infrequently attacked by ailments from
which one of their parents or grand-parents had previously suffered. In
spite of the emphasis that has recently been put on the facts of heredity,
the present tendency of preventive medicine holds out a larger hope by
impressing upon us the fact that in such affections, for example, as
tuberculosis and insanity, the individual's environment and personal
history are perhaps more potent than hereditary influence in the causation
or the prevention of disease.
DISEASES OF PLANTS. See _Plant Pathology_.
DISESTABLISHMENT, the severance of connection between Church and State,
with the resultant emancipation of the Church from civil control, is a
movement in which there has been considerable growth during the last
half-century. The Church of the West Indies was disestablished in 1868, and
all Colonial Churches, with the exception of the Church in India, are now
free from State authority. In 1869 an Act, taking effect two years later,
was passed for the disestablishment of the Church of Ireland, in which
country the mass of the inhabitants are Roman Catholics. In France all
recognition of Roman Catholicism as the State religion ceased in 1905, the
French Government now tolerating all religions. In 1914 was passed a Bill
for disestablishing the Church in Wales, though its effect was, owing to
the war, deferred till 1920 by the Suspensory Bill. The Church of Scotland
has been practically free from State control since 1874, in which year
patronage was abolished; and the presence of the Lord High Commissioner,
who represents the sovereign at the opening of the General Assembly, and
the precedence enjoyed by the Moderator during his term of office, are
little more than decorative courtesies. Among a section of the English
public there has been from time to time an agitation for the
disestablishment of the Church of England; and the movement is even said to
be viewed with favour by some advanced High Churchmen, who believe that it
would result in increased freedom for the adoption of their special views;
but, though a Disestablishment Society exists, there seems no immediate
prospect of a decisive step in this direction.
DISHONOUR OF A BILL, the refusal or neglect to accept or pay when due a
bill of exchange, or promissory note, or draft on a banker. It is
absolutely necessary that the holder of a dishonoured bill should give
immediate notice of the non-payment to the drawer or endorsers.
DISINFECTION, the means employed for killing the germs of infectious or
contagious disease by physical or chemical agencies. The former are the
more important, and consist in applying water or steam at the
boiling-point, or hot air at 160degC. Ten minutes' boiling, or half an hour
in hot air, kills all ordinary disease germs, but a longer exposure is
necessary to kill germs (especially those of putrefaction), which form
spores (see _Bacteria_). The most important chemical agents are chlorine,
iodine, carbolic acid, bleaching powder, Condy's red fluid (containing
permanganate of potash), perchloride of mercury, formalin, and flavine.
Carbolic acid is one of the most effective, needing, however, care in the
handling, as it is very poisonous and in strong solution causes severe
burns. It does not in its common form mix with water, but solutions can be
made by using hot water. A greater dilution than 1 part in 40 of water is
useless as a disinfectant. For application to the skin, tincture of iodine
is one of the readiest preparations. In cases of infectious disease the
most important points are the immediate disinfection of all the excretions
of the patient. Expectoration should be received into a sputum-cup
containing 1-20 carbolic acid, and all handkerchiefs when soiled should be
similarly treated. The personal linen and sheets of the patient should be
placed in carbolic acid (1-40) in a slop-pail, and should be boiled before
being sent to the laundry. All plates, spoons, &c., used for the patient's
food, should be boiled or scalded immediately after use. The excretions of
the bowels or kidneys should be treated with bleaching powder. Those in
attendance should wear an overall when in the sickroom, and should wash the
hands and face before coming into contact with anyone outside. They should
wash out the mouth frequently with Condy as strong as can be tolerated.
Their linen should be treated in the same way as that of the patient. At
the close of the illness all bedding should be baked in the hot-air oven
which most local authorities now provide for the purpose. Everything
washable in the sickroom should be washed with soft soap, and it is better
that the room should be repapered.
DISIN'TEGRATOR, a machine for pulverizing and sometimes for mixing various
materials, such as rock, asphalt, ore, artificial manures, sugars, corn,
and the ingredients of mortar.
DISLOCA'TION, a surgical term applied to cases in which the articulating
surfaces of the bones have been forced out of their proper places. The
particular dislocation takes its name either from the joint itself or its
farthest bone, and is called _compound_ when accompanied by an external
wound. The most common dislocations are those of the hip, shoulder, elbow,
knee, and ankle, and the chief obstacle to their reduction is the spasmodic
and violent contraction of the muscles consequent upon them, the
application of considerable force being often necessary to set the joint.
Chloroform is of great use, not only in preventing pain but in relaxing the
muscles. The most dangerous dislocations are those of the bones of the
spine.--In geology it signifies the displacement of parts of rocks or
portions of strata from the situations they originally occupied.
DISMAL SWAMP, a large tract of marshy land in America, beginning a little
south of Norfolk, in Virginia, and extending into North Carolina,
containing 150,000 acres; 30 miles long, from north to south, and 10 miles
broad. This tract was entirely covered with trees, with almost impervious
brushwood between them, but it has now in part been cleared and drained. In
the midst of the swamp is a lake, called _Drummond's Pond_, 7 miles in
length. A navigable canal through the swamp connects Chesapeake Bay and
Albemarle Sound.
DISPENSA'TION is the act by which an exception is made to the rigour of the
law in favour of some person. The Pope may release from all oaths or vows,
and may sanction a marriage within the prohibited degrees of the Mosaic
law, or exempt from obedience to the disciplinary enactments of the canon
law. In England the monarch claimed, in former times, a similar dispensing
power in civil law, but the prerogative was so much abused by James II that
it was abolished by the Bill of Rights. The power of commuting sentences in
capital cases is the only form in which the dispensing power of the Crown
still exists. In ecclesiastical matters a bishop may grant a dispensation
allowing a clergyman to hold more than one benefice, or to absent himself
from his parish.--Cf. F. W. Maitland, _Constitutional History of England_.
[Illustration: Winged Fruit
1, Ash. 2, Sycamore. 3, Hornbeam.]
[Illustration: Parachute Fruits
1, Ripe fruit of willow-herb, dehiscing. 2, Single fruit of clematis. 3,
Single fruit of dandelion.]
[Illustration: Hooked Seeds
1, Geum and single fruit. 2, Burdock.]
DISPERSAL OF SEEDS AND FRUITS serves (_a_) to scatter these reproductive
structures and so reduce internecine competition; (_b_) to bring the seeds
into new surroundings, which may be more favourable than those of the
parent plant. The chief agents of dispersal are wind and animals. Very
minute seeds, like those of orchids, are carried away by the gentlest
air-currents. Larger wind-borne seeds are _winged_, as in the pine, most
Bignoniaceae, &c.; or provided with a tuft of hairs acting as a
_parachute_, as in willow, willow-herb, cotton, &c. Winged _fruits_ are
exemplified by ash, elm, sycamore, many docks, &c.; parachute _fruits_ by
Compositae, Clematis, cotton-grass, &c. In the case of animal dispersal,
the whole fruit is usually involved, being either _edible_, with hard
indigestible seeds which are cast up or voided with excreta (fleshy
fruits), or _hooked_ so as to adhere to fur or wool, as in bidens,
cleavers, enchanters' nightshade, and other 'burs'. A small number of
fruits and seeds, such as the coco-nut and the seeds of water-lilies, are
adapted for water transport. In certain cases seeds are scattered for short
distances by an 'explosive' mechanism, as in wood-sorrel, impatiens,
sand-box tree, squirting cucumber, and other 'sling' fruits.
[Illustration: Explosive or Sling Fruits
1, _Ecbalium Elaterium_, flowers and fruit, one fruit detached from its
stalk and with its seeds squirting out. 2, _Oxalis Acetosella_, entire
plant, with one unripe fruit on a hooked stalk, and one ripe fruit on an
erect stalk ejecting its seeds. 3, Ripe fruit of _Oxalis Acetosella_
ejecting the seeds (enlarged).]
DISPERSION, in optics, the angular separation of light rays of different
colour, that is, of different wave-length. Dispersion may be caused either
by refraction or by diffraction. When a beam of composite light passes
obliquely from air into a second transparent medium, each constituent of
the light is bent or refracted through a different angle from the original
direction of the beam, with the result that the different colours are
separated fanwise, or dispersed at the surface of the second medium. In the
refraction spectrum of white light, when caused by passage through a glass
prism, the red rays are least deviated and the violet rays most deviated,
if we consider only the visible spectrum. The difference of the angles of
deviation for two selected rays measures their dispersion, and if this
angle is divided by the deviation of the mean ray, we obtain the dispersive
power of the prism. Transparent media vary in their dispersive powers; for
example, carbon disulphide has more than three times the dispersive power
of crown glass. The true nature of dispersion was first demonstrated by
Newton, who concluded that the colours of the spectrum were homogeneous and
caused by simple vibrations of definite wave-length, the different colours
being unequally refrangible. Newton was, however, led to the erroneous view
that the dispersion was proportional to the refraction. This was later
disproved by the construction of achromatic lenses, or lenses which caused
deviation without dispersion, and of direct-vision spectroscopes, or
instruments which caused dispersion with no deviation of the central part
of the spectrum. The dispersive power is not the same for all parts of a
refraction spectrum; besides, the same colours do not occupy the same
positions in spectra formed by prisms of different material. This arises
from the fact that there is no simple relation between the deviation of a
ray and its wave-length; consequently, such spectra are called irrational,
and the property is known as the irrationality of dispersion. In the
diffraction spectrum, the order of the colours is reversed, red undergoing
the greatest deviation; also, the deviation for a given colour is nearly
proportional to the wave-length. The diffraction spectrum is therefore
termed a normal spectrum.
All substances do not give the same order of colours in their spectra;
certain exceptions are known in which the usual order of the colours is
changed. Christiansen showed that an alcoholic solution of fuchsine gave a
spectrum containing only violet, red, and yellow; the violet is least
refracted, and the yellow most, and a dark band lies between the violet and
the red. This has been called anomalous dispersion, and similar effects
have been observed in iodine and sodium vapours, and in solutions of
colours derived from aniline which exhibit surface colour.
The theory of dispersion now generally accepted is that of Sellmeier, which
was published in 1871. Sellmeier assumed that when light waves pass through
a material substance, they set the particles of the substance in vibration,
and these resonant vibrations react in such a way as to modify the velocity
with which the waves are transmitted. Applying the dynamical principles of
wave motion to the case of an elastic solid in which heavy particles are
embedded, Sellmeier obtained an equation which connected the refractive
index of the substance with the wave-length of the incident light.
Equations of similar form were subsequently derived by Ketteler and
Helmholtz. The consideration of Sellmeier's equation leads to important
conclusions. If the period of vibration of the incident waves is very
short, as compared with those of the particles forming the solid, no
refraction will take place, and the rays will travel through the solid
without deviation and without change of velocity. This is verified in the
case of X-rays, which consist of extremely short waves and which are not
deviated on passing through light-opaque solids. Sellmeier's equation may
also be modified to apply to the case of anomalous dispersion. The
phenomenon is always associated with absorption of light of a particular
wave-length or range of wave-lengths, and the conclusion is drawn that the
medium will possess an abnormally high refractive index for waves slightly
longer than those which it absorbs, and an abnormally low index for waves
slightly shorter than those which it absorbs. This result has been verified
by various investigators. Rubens has determined the values of the constants
in Sellmeier's equation for rock-salt, sylvine, fluorspar, and quartz, and
has shown that the equation gives correct values for the refractive indices
of these substances over the entire range of wave-lengths to which they are
transparent.--BIBLIOGRAPHY: T. Preston, _Theory of Light_; E. Edser, _Light
for Students_; P. Drude, _Theory of Optics_.
DISPLACEMENT. The position of a point in space is fixed by means of its
distances x, y, z, from three mutually rectangular planes. If the point
moves to another position, it is said to be displaced, and the rates of
displacement parallel to these planes measure the velocities dx/dy, dy/dt,
dz/dt parallel to these planes. If the acting forces be resolved in
directions parallel to these planes, relations may be found between the
forces, the accelerations parallel to the planes and the mass of the body.
These relations are called the equations of motion. In hydrostatics a body
immersed in a liquid displaces a certain volume of the liquid, and the
upthrust of the liquid in the body is, by the principle of Archimedes,
equal to the weight of liquid displaced. It follows that, in the case of a
floating ship, the weight of the ship is equal to the weight of water
displaced. This weight is called the displacement of the ship, and is
measured in tons.
DISPOSITION, in Scots law, is, in its general acceptation, a deed by which
a person provides for the general disposal of his property heritable and
movable, after his death, equivalent to a will or testament; also a
conveyance of property.
DISRAELI, Benjamin. See _Beaconsfield_.
D'ISRAELI (diz-r[=a]'e-li), Isaac, man of letters, and father of the
well-known statesman, was born at Enfield, Middlesex, in 1766, died in
1848. His father, Benjamin D'Israeli, a descendant of a family of Spanish
Jews which had settled at Venice in the fifteenth century to escape the
Inquisition, came over to England in 1748 and made a large fortune. Isaac
D'Israeli, however, showed a strong repugnance to commerce, and was finally
permitted to follow his literary bent. An anonymous reply to Peter Pindar,
entitled _On the Abuse of Satire_, was followed during 1791 to 1793 by the
appearance of his _Curiosities of Literature_, the success of which
determined much of his afterwork. His _Essay on the Literary Character_ was
published in 1795, and some time afterwards a volume of romantic tales,
_The Loves of Mejnoun and Leila_. Between 1812 and 1822 appeared his
_Calamities of Authors_, _Quarrels of Authors_, and _Inquiry into the
Literary and Political Character of James I_; the three being afterwards
published collectively under the title of _Miscellanies of Literature_. In
1828 appeared the commencement of his _Life and Reign of Charles I_, a work
completed in 1831. An affection of the eyes put an end to a projected _Life
of Pope_ and a _History of English Freethinkers_, but in 1841 he published
a selection from his MSS. under the title of _Amenities of Literature_. The
greater part of his life was passed in his library. For his son, see
_Beaconsfield_.
DISRUP'TION, the name commonly applied in Scotland to the act by which, in
1843, 474 ministers and professors of the Established Church gave up their
livings to vindicate principles which they held to be essential to the
purity of the Church, and in harmony with its earlier history. See _Free
Church_.
DISS, a town, England, Norfolk, on the slope of a hill 18 miles south by
west of Norwich. It was formerly noted for the manufacture of 'Suffolk
hempen cloth', worsted yarn, and knit hosiery. Pop. 3763.