Francis Lieber.

Library of universal knowledge. A reprint of the last (1880) Edinburgh and London edition of Chambers' encyclopaedia, with copious additions by American editors (Volume 13) online

. (page 65 of 203)
Online LibraryFrancis LieberLibrary of universal knowledge. A reprint of the last (1880) Edinburgh and London edition of Chambers' encyclopaedia, with copious additions by American editors (Volume 13) → online text (page 65 of 203)
Font size
QR-code for this ebook

substance, as wood, it would for each turn advance
as much as the center of the blade (or thread) had
moved along the spindle in forming the screw,
i.e., the distance ab. If, on the other hand, the
screw itself were prevented from moving longi-
tudinally, and the piece of wood not fixed, the latter
would be compelled to advance along the screw
the same distance ab. When the screw is fixed
beneath a ship, and made to revolve in the water,

the case lies between the two just supposed, the screw moves forward, and with it the
ship, and the water in which it has been working moves backward. The backward
motion should only be small proportionately, and the ratio between it and the sum of
the backward motion of the water and the forward motion of the ship is called the slip,
which in well-designed vessels has a value of from 0.1 to 0.25.

It is obvious also that on the same spindle there may be more than one blade, pro-
vided that all the blades have the same pitch or rate of progression along the spindle (in
fig. 1 ab is the pitch of the screw-). Screws have thus been formed with two, three, four,
and six blades or arms, but the form most commonly used is two blades for ships of
war. and three or four blades in the merchant service.

If the screw be cut off before attaining the length ab of a whole convolution, as at c,
the portion ac will still retain all the properties of the screw. In the earlier attempts
ecrews were tried of the length of a
whole convolution, or even two whole
turns; but experiment has since
shown that this length is a disadvan-
tage. The best results are obtained
when the sum of the lengths, measured
parallel to the center line of the shaft
of all the blades, is equal to about 0.4
of the pitch. This holds equally
good for two, three, or four bladed
propellers, so that if n equals the
number of blades, then the length of
one blade, or at, would be expressed

. .. 0.4 ab ' ,
by the equation ac = . A four-

bladed screw of this kind, and of a
form very generally used in the mer-
chant navy, is shown in fig. 2.

The following are the technical terms applied to the screw-propeller: The shaft ia

FIG. 1.



FIG. 2.



the cylindrical axis on which the screw revolves, and is the medium for communicating
to it the power of the steam-engine; the blade is the thread of the screw; the pitch, the
length of shaft on wb.'oh the blade would make one complete turn; the diainikr is
the distance between thn tips of opposite blades; and the length is the distance from tho
front to the back edge of blade projected upon a fore and aft plane.

The application of the screw to the propulsion of a vessel through the water is not
new. In 1S02 Dr. Shorter, an English mechanician, produced motion by its agency;
but liis discovery was valueless, as the steam-engine had not then bceu practically
i >plied to navigation. Those who first employed Watt's engine on board ship adopted
l ie paddle-wheel, the success of which turned attention from the screw for nearly thirty
} -ars. At length, in 1832, Mr. B. Woodcroft patented a screw-propeller with an increas-
ing pitch ; and four years later, Mr. F. P. Smith patented a screw making two whole
turns, which he reduced in 1839, to one whole turn. In 1837 he and cap. Ericsson, an
American inventor, brought the matter practically forward on the Thames, where a
small screw-steamer, 45 ft. long, 8 ft. broad, and of 27 in. draught, towed the Toronto of
630 tons against tide at 4i knots an hour. In 1839 an American gentleman had the
Robert Scockton built for him by Messrs. Laird, with which he reached America. The
British admiralty, however, refused any support to the new propeller, until the success
of the Archimedes, built in 1838, of 233 tons and 80 horse-power, which was exhibited
at the principal ports, rendered opposition no longer possible. The admiralty, then, as
an experiment, constructed the Rattler, from the trials of which vessel many valuable
data lor the screw-propeller have been derived. Meanwhile, in 1838, Mr. James Lowe
had shown that the length of the screw should not exceed th of the pitch; and after
actual and successive trials, the screw of the Rattler was cut down from 5 ft. 9 in. to
1 ft. 3 inches. These experiments established the screw as a rival to the paddle-wheel;
and its advantage for ships of war became incontestable, as, from the entire submer-
gence of the propeller, and consequent lowness of its engines in the ship, the chances
of injury from an enemy's shot were reduced almost to nothing. Some of the great
Bteam-companies notably the Peninsula and Oriental company also patronized it,
smd it was found of great value as an auxiliary in sailing-vessels. The result is that,
at this time, its use in the British navy is almost universal, except in cases where want
of sufficient denth of water, or other special circumstance, causes the paddie-whec.1 still
to be employed.

Several varieties of screw have been introduced, each finding many supporters. The
one which was for many years used in the British navy was invented by Mr. R. Grif-
fiths. In it the blades, in place, of rising from a small boss, as in fig. 2, spring from a
i ollow sphere occupying the screw's diameter. This arrangement was adopted because
experiment proved that the central portions of the blades of the ordinary screw absorb
ibout 20 per cent of the propelling power, while the}' produce little useful effect, from
Ihe circumstance that at that part (especially in screws of a coarse pitch) the blade is
nearly in a line with the shaft, and acts at" right angles on the water, causing only a
disturbance of that portion on which the outer and more powerful end of the blade
operates. The globe, on the other hand, revolves with little friction. A further im-
provement was effected by bending the tips of the blades a little over backward, so
that the face of the blade striking the water was partly convex. The older propellers
Lad blades which increased in width uniformly from boss to tip. These were found to
create much vibration in the ship, and the "leading" corner is therefore rounded away.
as shown in fig. 2. This is also done in Grifnths's propeller, but he probably carries the
principle to excess in cutting away also the " following" corner, and so lessening the
effective surface of the blade. A propeller invented by Mr. Hirseh, and known by his
name, has been lately successfully tried by the Admiralty, and may probably be much
used by them in future.

One difficulty in the use of the screw as an auxiliary in sailing-ships is that in a
good wind the screw seriously impedes the sailing. To prevent this, various devices
are resorted to. In some cases, the screw is disconnected from the shaft, and left to
revolve freely; in others, as in most ships of war, it is disconnected and hoisted alto-
gether out of the water by means of an iron framework worked above the screw in a
sort of well. Messrs. Maudslay have patented a " feathering-screw," which, by a simple
apparatus, can, when the steam-power is not required, have the blades turned into a
line with the ship's keel, and the screw (which must be two-bladed) fastcned-in a verti-
cal position. When thus treated, the screw is out of danger, and forms no impediment
to the ship's progress.

The usual position for the screw is immediately before the stern-post, the shaft on
which it revolves passing, parallel to the keel, into the ensine-room. Many vessels
Lave been built, especially by Messrs. J. & W. Dudgeon, of London, with two screws,
one under each quarter. These have independent action, and as one can therefore be
reversed while the other goes ahead, great steering-power is imparted; so much so, that
vessels constructed on this principle are said to be able to turn in their own length. For
a given power, a twin-screw vessel draws less water, owing to the lessened diameter of
the propellers, than an ordinary screw-steamer. As the action of the screw depends on
the comparative immobility of the water in which it acts, it is necessary, for the develop-
ment of its full power, that it should be completely immersed, and that there should be


nearly 2 ft. of \vatcr above the top of the upper blade. It follows from this that, ceteris
paribus, the screw-vc-sel will draw more water than the paddle-Steamer; for in large
steamers the screw id frorfr 15 to 18 i't. in diameter, and in the Great Eastern it
reaches C4.

it now only remains to notice the comparative advantage of the paddle and screw.
Under favorable circumstances, in .ships of equal touuage and power, there is little dif-
ference in speed or force. Before the wind, tiie paddle has a slight advantage; with
the wind ahead, the resistance offered by the paddle-boxes transfers the advantage to
tli'.: screw. Fastened stern to stern, the screw-ship drags the paddle-ship; but fastened
bow to how, the same result is not found. This is, however, rather to be attributed to
the loss of power in a paddie ship when not in progress (see PADDI.K WHEEL), than to
an}' actual superiority of screw. In a long voyage, .however, the gain is distinctly with.
the screw; becau-e the weight of fuel borne at starting sinks the paddles too low in the
water, and probably its exhaustion at the end of the voyage deprives them of their
proper dip; whereas with ordinary management, the screw will always be immersed.
Again, rolling deprives the paddle of much power; while pitching deprives tiie screw
of it* prop-T matrix; but the balance of loss in tempestuous weather is iii favor of the
screw. It has been already shown that in men-of-war the scew is the most useful agent;
and a- an additional reason may be adduced the clear broadside which it allows lor the
guas. Ou the other hand, in point of comfort to the passengers, the advantage lies
unquestionably witli the paddle; for the rapid revolution of the heavy screw on a shaft
extending half the ship's length, produces a continuous as id very unpleasant vibration;
while the lower position of the engines and screw gives the vessel a deep roll. For
lakes and rivers, where the water is smooth and the voyage short, paddles are best, and
more especially so when the water becomes often shallow or is choked with weeds,
which would soon clog the screw.

In scientific language the motion of a vessel by means of a screw, is said to be due
to the forward reaction of the water in which the propeller revolves upon the blades,
and through them upon the whole vessel. In order that this useful reaction may bear
the largot pos-ible ratio to the work done by the engine, it is essential that the form of
the ship aft should be such as will secure that plenty of water shall always have access
to the forward side of the screw as the vessel goes along. This has been demonstrated
by the experimental alterations in the after-body of the Dwarf (1846), and still more
strikingly by placing a disk of the same diameter as the prop"ller in front of it. If the
propeller be worked in these circumstances, the vessel will not move forward at all,
although the power given out by the engines rcnuins as before.

SCREW-WRENCH, a tool used for grasping the flat sides of the heads of large screws,
such as are used in engines and other large work-;. The heads are usually octagonal
laterally, and the wrench is made of two portions like hammers sliding one upon the
other, so that screw-heads can be grasped of different sizes, and the handle forms the
lever by which they are turned round. The screw-key is only a more simple kind of
wrench, which will only act upon screws of two sizes, iittin^ the jaws at each cad.


SCRIBE (lleb. &>ffr; Gr. Qrammateus, NomodidasJajlos), among the .Tews, originally a
kind of military oilicer, whose business appears to have been tlie recruiting and organ-
izing of troops, the levying of water-taxes, and the like. At a later period, 'especially at
the time of Christ, it had come to designate a learned man, a doctor of the law. Cliri<t
himself recognizes them as a legal authority (Matth. xxiii. 2); they were the preservers
of traditions, an 1 formed a kind of police in the temple and synagogues, together with
the high-priests; and the people reverenced them, or were expected to reverence them,
in an eminent degree. They were to be found all over the country of Palestine, and
occupied the rank and profession of both lawyers and theologians. Their public field
of action was thus probably threefold: they were either assessors of the sanhedrim, or
public teachers, or administrators and lawyers. Many of these teachers had special
class-rooms somewhere in the temple of Jerusalem, where the pupils destined to the
calling of a Rabbi sat at their feet. The calling of a scribe being gratuitous, it was
incumbent upon every one of them to learn and exercise some trade. Those scribes
who were not eminent enough to rise to the higher branches of their profession, to enter
the sanhedrim, to be practical lawyers, or to hold schools of their own. occupied them-
elves in copying the book of the law or the prophets, in writing phylacteries con-
tracts, letters of divorce, and the like. Their social position was naturally in accord-
ance with their talents and their importance. The apostles, not learned enough, for the
most part, to be scribes, are promised to become "scribes" of the kingdom of God, etc.

SCRIBE, ArorsTix EUGENE, a French dramatic writer, son of a wealthy silk mercer
of Paris, was born in 1791. Educated for the le^al profession, lie soon deserted it for
dramatic authorship. His first piece, /.>* Ih />;*, written by him in conjunction with
Germain Delavignc (brother of Casiniir Dclavigne). was played in 1S11. but til! 1816 he
cannot be said to have achieved n decided success. Since that time, pieces elm-fly
vaudevilles, from his pen have followed each other with the most astonishing rapidity;

Scribing. QQO


and in such demand were they at the hand of theatrical managers, that Scribe estab-
lished a sort of dramatic manufactory, in which numerous ytUaborateurs were constantly
at work, under his supervision. His plots are interesting, and his dialogue, light and
sparkling; and not a few of his pieces have been adopted for the English stage. Scribe
also wrote various novels, and composed the libretti for a considerable number of well-
known operas, including Masa niello, Fra Diavolo, Robert le Diable, and J,< : * JLnyncnots.
He was admitted a member of the French academy in 1884, and died Feb. 20, 1861.

SCRIBING, iu joinery, fitting the ends of pieces of wood together, so that the fibers
i .iy be at right angles, and the end cut away across the fibers.

SCRIBNER, CHARLES, 1821-71, b. New York; grandson of a Presbyterian minister;
educated at the university of New York, and Princeton college, where he graduated in
1840. He studied for the bar, but on account of feeble health, did not begin practice.
In 1846 he formed a partnership with Isaac D. Baker in the book-selling and publishing
business in New York, and published the works of Headley, Willis, Mitchell ("Ik
Marvel"), Dr. Holland, McCosh, Dr. Bushuell, etc. In 1857 the firm associated with it
Mr. Charles Weli'ord.and entered heavily into the importation of books from England: it
also entered extensively into the manufacture of educational books, and in 1870 estab-
lished Scribner's Monthly, which under the editorship of Dr. J. G. Holland, achieved
great popularity. On the death of Mr. Scribner, in 1871, the firm was re-orgaiftzcd
under the name Scribner, Armstrong & Co.

SCRIP is a certificate (usually about the size and appearance of a bank-note) of a per-
son's share or shares iu a joint-stock undertaking. It is issued on the party signing a
contract of copartnery, and is retained by him until an act of the legislature, or some
other formality, establishes the company, and authorizes the opening of regular books
for entering the name of shareholders- and the transfer of stock. In many instances
scrip is unauthorizedly sold, and made an object of speculation; the party to whom it
v. T as assigned, however, remains bound by the contract which he has subscribed, until
relieved of his obligations by transfer in the company's books.

SCRIYEN, a co. in e. Georgia, adjoining South Carolina; bounded on the e. by the
Savannah river, on the s.w. by the Ogeechee river; crossed by the Central railroad of
Georgia; about 780 sq.m. ; pop. '70, 9,175 4.888 colored. The surface is level. The
soil is sandy. The principal productions are com and cotton. Co. seat, Sylvaiiia.

SCRIYE'NER, FREDERICK HENRY AMBROSE, I.L.D., b. England, 1813; graduated
/at Trinity college, Cambridge, 1835; became assistant-master of the King's school, Sher-
borne; curate of Sand ford, Orcas, Somerset, in 1839; was appointed head master of Ful-
mouth school in 1846; rector of Gerrans, Cornwall, in 1861; in 1870 one of the English
company of revisers of the authorized version of the New Testament. He has published
A Supplement to the Authorized Version of the New Testament; A Collation of about
Twenty Manuscripts of the Greek Testament deposited in England; Contributions to (ha
Criticism of the New Testament, being the Introduction to the Codex Aug-ternis and Fifty
other Manuscripts.; Novum Testamentum Grcecum, text of Stephens of 1550, with Various
Readings of Beza, Tischendorf, 2regelles, etc.; Plain Introduction to tJie Criticisms of the
New Testament.

SCRIYE'NER'S PALSY, or WRITER'S CRAMP. A nervous disorder whose location
is in the motor nerves of that part of the hand usually engaged in holding the pen. It
is accompanied by pain and by symptoms of paralysis, which in some cases it practically
is. Under its influence the muscular movements of the thumb and forefinger become un-
controllable; and if the effort to write be continued, despite the warning symptoms, the
writing is illegible, while the disorder is increased. Of late years it has become much
the custom with those who are professional writers to hold the pen between the fore and
middle fingers, thus avoiding the strain on the muscles and nerves of the thumb, and
gaining a better support for the pen itself than is afforded by the old conventional
method so tenaciously adhered to by writing-masters. The treatment of writer's cramp
includes rest and a stimulating diet, tonics, especially iron, with sometimes the applica-
tion of a galvanic current to the part involved, and sometimes the use of strychnine, by

SCROF'ULA, or SCROPIIULA. was, \intil the last quarter of a century, regarded as con~
f -ting essentially of indolent glandular tumors, occurring frequently in tho neck, sup*
j irating slowly and imperfectly, and healing with difficulty. Recent pathologists,
I.owcvcr, have given a more extended meaning to the word scrofula. According to them
it signifies a certain disease or defect of the constitution, in which there is a tendency to
the production and deposition of a substance called tubercle in various tissues and
organs; and tubercle must thus be regarded as the essential element of scrofula. It
does not follow, however, that a deposit of tubercle should actually occur in every case
of scrofula. The tendency is present, and the absence or presence of the deposit depends
upon the extent of the affection, and is determined by various causes.

Sir James Pagct, one of our most eminent pathologists, very clearly sums up what is
generally understood by scrofula in the following paragraph: "It is a state of constitu-
tion distinguished in some measure by peculiarities of appearance even during health,


tmt much more by peculiar liability to certain diseases, including pulmonary phthisis.
TJi) chief of these '-scrofulous" diseases are various swellings of the lymphatic glands,
arising from causes which would be inadequate to produce them in ordinary healthy-
persons. The swelling are due sometimes to mere enlargement, as from an increase of
natural structure, sometimes to chronic, inflammation, sometimes to an acute inflammation
or abscess, sometimes to tuberculous disease of the glands. But beside.s these, it is usual to
reckon as "crofulous" affections certain chronic inflammations of the joints; slowly pro-
gressive "carious" uk orations of bones; chronic and frequent ulcers oa the cornea, oph-
thalmia (q. v.), attended with extreme intolerance of light, DUt with little, if any, of the ordi-
nary consequences of inflammation; frequent chronic abscesses; pustules, or other cutane-
ous eruptions, frequently appearing upon slight affection of the health or local irritation;
habitual swelling and catarrh of the mucous membrane of the nose; habitual swelling
of the upper lip." It is obvious that although the above-named forms of disease are
often more or less coincident, they have nothing sufficiently in common to justify tho
general appellation of scrofulous. They are certainly not all tuberculous diseases, and
hence sir James Paget doubts whether the proposal to make scrofulous and tuberculous
commensurate terms is practical, since the former, as generally employed, has a much
wider significance than the latter.

The word is derived from the Lat. scrofa, a sow, it being supposed that this animal
\vas especially liable to tumors such as occur in this disease. The Greek and Arabic
names for the disease are similarly derived from the words signifying "swine" in these
languages. AVliile ecrcfula'W&a the popular, stru ma (supposed to be derived from strito,
I heap up) used by Celsus, Pliny, and other Latin writers, was the classical name for
the disease. The vulgar English name, the king's evil, is derived from the long-cherished
belief that scrofulous tumors and abscesses could be cured by the royal touch. Multi-
tudes of patients were submitted to this treatment, and, as the old historians assert, with
perfect success, from the time of Edward the confessor to the reign of queen Anne. The
writer of the article "scrofula" in ihe English Cyclopaedia, mentions the curious historical
facts that " the old Jacobites considered that this power did not descend to Mary, Will-
iam, or Anne, as they did not possess a full hereditary title, or, in other words, "did not
reign by divine right. The kings of the house of Brunswick have, we believe, never put
this power to the proof; and the office for the ceremony, which appears in our liturgy as
late as 1719, has been silently omitted. The exiled princes of the house of Stuart were
supposed to have inherited this virtue. Carte, in the well-known note to the iirst vol-
ume of his History of England, mentions the case of one Christopher Lowel, who, in
1716, went to Avignon, where the court was then held, and received a temporary cure-,
and when prince Charles Edward was at Holyroodhouse in Oct., 1745, he, although only
claiming to be prince of Wales and regent, touched a female child for the king's evil,
who iu 21 days is said to have been perfectly cured." The practice was introduced by
Henry VII. of presenting the patient with a small coin (gold or silver). The French
kings also touched for the "evil." the practice being "traced back to Clovis, 481
A.oT On Easter Sunday, 1686, Louis XIV. is said to have touched 1600 persons using
the words: Le roy te louche ; Dieu te guerisse (the king touches thee; may God cure '.hie).
See Chambers's Book of Days, i. 82. The literature of this curious subject is somewhat
extensive. The reader who wishes to pursue the inquiry further is referred to Tooker's
Charisma, sire Domirn Sanctions, etc., 1597; Browne's Charisma Baxi'icon, or the Royal
Gift of Healing Strumcus, etc., 1684; and Beckett's Free and Impartial Inquiry into the
Antiquity and Efficacy of Touching for the King's Evil, 1722. The subject is also ex-
amined by bishop Douglas in his Criterion, or Miracles Examined, 1754; by Colqidioun,
in his Ins Rerelata, 1836 (who attributes the cure to animal magnetism); and by Howitt
in his History of the Super-natural in all Ages and Nations, 1863.

Scrofula is a disease of early life, and when it does not exhibit any of its manifesta-
tions before the period of maturity it seldom shows itself afterward.

In all systematic descriptions of this disease, two varieties of the scrofulous habit or
diathesis are given, viz., the sanguine or serous, and the phlegmatic or melancholic. la
the sanguine, there is a general want of muscular development, the limbs being soft and
flabby; the skin is fair and thin; the features are delicate, the rosy hue of the checks

Online LibraryFrancis LieberLibrary of universal knowledge. A reprint of the last (1880) Edinburgh and London edition of Chambers' encyclopaedia, with copious additions by American editors (Volume 13) → online text (page 65 of 203)