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EARLY

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ing that they might endanger his professional standing, he withdrew the edition from the market very soon after its publication. The same year appeared his "Visit to 13 Asylums for the Insane in Europe." In 1848 he published the "History, Description, and Statistics of the Bloomingdale Asylum." After his return from his second European tour, he published in the "American Journal of Insanity series of articles on institutions for the insane in Germany and Austria, which were subsequently collected in a volume. Another series of articles on "Bloodletting in Mental Disorders" was also published in book form in 1854. His other contributions to the medical and psychological journals are very numerous. -THOMAS, & writer on law, brother of the preceding, born in Leicester, Mass., April 21, 1791, died in Philadelphia, July 14, 1849. His early education was obtained at the academy of his native town. In 1817 he removed to Philadelphia, and engaged in mercantile pursuits for a few years, and then having studied law commenced the practice of the profession in that city, where he was distinguished not only for legal ability, but for the large amount of time he bestowed without fee or reward in defending the cause of the poor, often refusing cases offering large pecuniary emolument in order to attend to those who were unable to pay. He edited in succession the "Columbian Observer," "Standard," "Pennsylvanian," and "Mechanics' Free Press and Reform Advocate;' and he took an active part in calling a convention to revise the constitution of Pennsylvania in 1837, was a prominent member of it, and is believed to have made the original draft of the new constitution. At this time he was so popular that any office in the gift of the people was at his command, but he lost the support of the party with which he was connected (the democratic) by advocating the extension of the right of suffrage to negroes. In 1840 he was the candidate of the liberty party for the vice-presidency. After that period he mingled little in political affairs, and devoted himself almost entirely to literary pursuits. His first published work was an "Essay on Penal Law," written while he was a member of the law academy of Philadelphia, and published by the library company. This was followed by an "Essay on the Rights of States to alter and annul their Charters," a work which elicited the approbation of Thomas Jefferson; a "Treatise on Railroads and Internal Communications," published in 1830; a spelling book for schools, which was highly approved by eminent teachers in Philadelphia and vicinity; a "Life of Benjamin Lundy," an eminent philanthropist. At the time of his death he had nearly completed a history of the French revolution and a translation of Sismondi's "Italian Republics."

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EARLY, a S. W. co of Ga., bordering on Ala., bounded W. by the Chattahoochee river, and N. by Colamoka creek; area, 864 sq. m.; pop. in 1852, 8,641, of whom 4,211 were slaves.

EARTH

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The surface is a fertile plain, watered by Spring creek and several of its branches, and occupied by corn and cotton plantations, interspersed with forests of oak and yellow pine. Scarcely a rock is to be seen in the county. The Chattahoochee is navigable along the border of the county by steamboats, and the smaller streams furnish good water power. On the bank of Colamoka creek is one of those remarkable ancient mounds which have been found in various parts of the United States. It is 75 feet high, with a level surface on the top 240 by 90 feet in extent. The productions of the county in 1850 amounted to 4,354 bales of cotton, 223,037 bushels of Indian corn, and 76,377 of sweet potatoes. There were 16 churches, 1 newspaper office, and 144 pupils attending academies and schools. Value of real estate in 1856, $994,031. Named in honor of Peter Early, governor of Georgia in 1813. Capital, Blakely.

EARLY, JOHN, a bishop of the Methodist Episcopal church south, born in Virginia in 1785. At an early age he joined the Virginia conference, and became an itinerant minister. He filled successively the offices of secretary of conference, presiding elder, and delegate of the general conference. At the general conference of 1846 he was elected general book agent, in which office he continued until elected bishop in 1854. As a traveller, revivalist, and systematic preacher, it is said of him that he has few equals in the ministry of the southern Methodist church.

EARTH, the planet upon which we live. (For its motions and its relations to the heavenly bodies, see ASTRONOMY.) The ancients, familiar with only a small portion of its surface, entertained the crudest notions of its form and extent. In the time of Homer it was regarded as a flat circle, everywhere surrounded by a dark and mysterious ocean. The nations which dwelt upon its borders were called Cimmerians and described as living in perpetual darkness. In every direction the most distant lands heard of were placed on the margin of this ocean, so that as geographical knowledge increased its shores in like manner receded. The strait at the pillars of Hercules, leading into the ocean, was for many centuries the boundary of the earth toward the west. The Black sea appears for a time to have been the boundary in the other direction, and Colchis on the margin of the Eastern sea. Ethiopia reached the sea to the south. and the Riphæan mountains stretched to the northern verge of the earth. The ancient Hebrews found the same boundary to the west; but in other directions they vaguely spoke of the "ends of the earth." Availing themselves of the commercial enterprise of the Phoenicians, they had in the time of Solomon prosecuted their trading voyages through the straits of Babelmandeb into the Indian ocean, bringing home from expeditions of 3 years' duration the products of tropical regions; while their ships sent westward toward the Atlantic returned laden with the tin, silver, lead, and other metallic products of Spain and Great Britain. The ex

peditions of Alexander into Asia opened new of a degree upon the surface of the earth, and countries in the east, and largely extended the from this to calculate the whole circumference. geography of the Greeks. The Romans by their At Syene, in upper Egypt, was a well, at the conquests added discoveries in the other direc. bottom of which the full disk of the son was tion; but these, while they removed further off, seen at noon of the day of the summer solstice; still served to fix the encircling ocean, the mare at the same time from Alexandria, then taken tenebrosum, as the impassable barrier and limit to be on the same meridian, its angular distance to the land. At a very early period the astron- from the zenith was 7° 12'. This was the omers among the Egyptians, Chaldeans, and measure of the celestial arc between the two Greeks perceived that the heavenly bodies, zeniths, and bore the same relation to the whole while occupying the same positions, stood in dif- circumference as the distance between the two ferent relations to different points upon the sur- points on the surface bore to the circumference face of the earth. In the school of Thales, Anaxi- of the earth. Presuming this distance to be mander, Anaximenes, and Pythagoras, the sun 5,000 stadia, and 7° 12' being zo of a circle, the dial was employed to mark the progress of the total circumference was then 250,000 stadia. sun in its meridional range, and to determine the The world known by the reports of travellers latitude of places, and the division of the year into extended only about 38,000 stadia in a N. and S. 365 days. The length of the longest and shortest direction; and from the pillars of Hercules to days at numerous places was determined by the the city of Thinw upon the eastern ocean, along Egyptians with this instrument, and they first his base line drawn E. and W. across the Mediadded 57 days to the older division of the year terranean, Eratosthenes reckoned a greatly exinto 360 days. Thales (born at Miletus, 640 B. aggerated distance of 70,000 stadia, and yet less C.) perceived the error of giving to the earth a than 1 of the whole circumference. He indulges plane surface, and ascribed to it a spherical fig- only conjectures whether the remainder was ocure and a position at the centre of the universe. cupied entirely by the ocean he called the AtAnaximander believed it was cylindrical; and lantic, or consisted in part of strange continents in the Pythagorean cosmography the extraordi- and islands. Posidonius next attempted a siminary advance was made of placing the sun in lar measurement by observations of the altitude the centre of the system with the earth moving of the star Canopus, when seen on the meridian about it. But this step was soon lost, and the at Rhodes, and again at Alexandria. Finding a knowledge of the extent and form of the earth difference of altitude of 7° 30', and assuming made but slow progress as the limited observa- the meridional distance of the two points to be tions of travellers were gradually accumulated. 5,000 stadia, he made the whole circumference A latitude observation is recorded of Meton and 240,000 stadia. Of the real value of the stadium Euctemon at Athens, 432 B. O. As commercial employed we are entirely ignorant; and it is intercourse was extended among the nations and certain that it was not, as employed at that time, navigation became an important art, the spher- a fixed determinate measure. The great astronical figure of the earth must have become appar- omer Hipparchus of Rhodes, born at Nice, in ent by the same phenomena which are now com- Bithynia, 140 B. O, first determined the longimonly appealed to in proof of it, viz.: the sinking tudes of places upon the earth by the eclipses of distant objects seen upon a level plain, as the of the moon, and produced maps upon which sea below the horizon; the greater or less ele- localities were designated by their latitudes and vation of the circumpolar stars, as the observer longitudes. Thus & means was furnished of is further toward the north or the south; the determining the relative positions of places different angles under which the sun is seen at without the necessity of measurements upon the noon of the same day at different points on the surface between them; and afterward, when same meridian; and other appearances of the suitable instruments should be contrived, of same character. This form being recognized, it finding directly any spot beyond the sea, and was natural to seek the measure of its circum- returning to the starting point. Adopting these ference, and it is extremely probable that at- principles, Ptolemy, the astronomer and geogtempts of this kind were made before any of rapher, prepared the most complete map of the those of which we have account. Some of the world so far as it was known, designating places measures of the most remote antiquity appear by their latitudes and longitudes, and cansing to have relation to the terrestrial circumference; the meridians to approach each other toward and, as stated by Laplace, they seem to indicate the pole. For want of accurate measurement not only that this length was very exactly of the length of a degree, his map, however, was known at a very ancient period, but that it has very imperfect. Still it continued for many also served as the base of a complete system of centuries to be the great authority in geography; measures, the vestiges of which have been found and it was not until 1635, when the difference in Asia and Egypt.” Aristotle states that be- of longitude between Marseilles and Aleppo was fore his time the circumference had been detere found to be only 30° in place of 45°, as repremined by mathematicians at 400,000 stadia. sented upon the map, it became apparent that Eratosthenes, who lived the next century after more perfect observations for longitudes must Aristotle, appears to have been the first to be adopted than those of the ancients. The clearly perceive the true method of applying uncertainty of the results obtained by observing astronomical observations to the measurement eclipses of the moon was soon perceived, and at

EARTH

last the suggestion of Galileo was adopted of observing the eclipses of the satellites of Jupiter. In the 9th century an attempt was made by direction of the caliph Al Mamun, who reigned at Bagdad from 813 to 833, to determine the length of a degree of latitude. His mathematicians assembled on the plain of Shinar, and, taking the altitude of the polar star, separated in two parties, travelling in opposite directions till they found a difference of altitude of one degree. They made the distance upon the surface the same as that given by Ptolemy, probably adopting his conclusion, which they were set to verify. From this time to the middle of the 16th century no further attention was given to ascertaining the dimensions and true figure of the earth by astronomical observations; but vast accessions of geographical knowledge were made by the enterprise of the navigators of this period. They at last solved the mystery of the mare tenebrosum. The next attempt to determine the circumference was made by Fernel, a French physician, who died in 1558. In the want of exact surveys, by which the true distance between places might be known, he measured the space between Paris and Amiens by the number of revolutions of his carriage wheel, and making his observations for latitude he made the length of a degree 57,070 French toises; a remarkably close approximation to the actual length. Willebrord Snell, a mathematical teacher of Holland, made in 1617 a similar attempt between Alkmaar and Bergen-op-Zoom; and he was the first to apply a system of triangulation to expedite his geodetic measurements. His instrument for observing angles was a quadrant of 5 feet radius. As afterward corrected by Muschenbroek, the length was 57,033 toises. In 1635 Norwood in England repeated the experiment, measuring along the road the distance between London and York, making the degree 367,176 feet, or 57,800 toises. Toward the close of the same century Picard first applied the telescope attached to a quadrant, and furnished with cross wires, to observe the angles for his triangulation, and twice measured between Amiens and Malvoisine with wooden perches a base of 5,663 toises, or nearly 7 m. in length, employing also at the other extremity a base of verification of 3,902 toises. The celestial arc of 1° 22′ 55′′ was measured by a sector of 10 feet radius. He made the degree 57,060 toises, a result very nearly accurate, attained by a fortunate compensation of errors in his method and in his standard of measure. In 1718 the second Cassini published a work upon the magnitude and figure of the earth, with an account of measurements further north and south on Picard's line made by La Hire and himself. About the time of Picard's observations the question began to be agitated, whether the form of the earth was really that of a true sphere. The tendency of the centrifugal force of bodies revolving upon their axis, established by Huyghens and Newton, must evidently be to throw their movable particles from the poles toward

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the equator and there accumulate them in a belt, increasing the equatorial diameter. Newton calculated that to maintain the hydrostatic equilibrium the proportion of the polar to the equatorial diameter must be as 230 to 231. Richer, who was sent by the academy of sciences of Paris to Cayenne in 1672, observed that the pendulum which vibrated seconds in Paris lost about 2 minutes daily at Cayenne. This fact, as Newton explained in his Principia, must be a consequence of the reduction of the force of gravity, either by effect of the centrifugal force or of increased distance from the centre. The deductions of Newton and Huyghens that the earth was a spheroid like that already observed of Jupiter, flattened at the poles, conflicting with the opposite conclusions of the first Cassini, induced the academy of sciences to cause exact measurements of meridional arcs to be made both near the equator and the polar circle. The celebrated commission of their members left Paris in 1735, Bouguer, La Condamine, and Godin to join in Peru the officers appointed by Spain, Antonio d'Ulloa and Jorge Juan; and Maupertuis with 4 others to proceed to the gulf of Bothnia, where they were joined by the Swedish astronomer Celsius. Ten years were spent by the party in Peru in the measurement of an arc of over 3° in length, extending from lat. 2' 3" N. to 3° 4' 32" S. In 2 measurements of the original base the difference was hardly 24 inches; and a second base of 5,259 toises differed when measured less than a toise from its length as calculated from the triangles. The length of the degree at the equator, reduced to the level of the sea, was calculated by Bouguer at 56,753 toises, or 362,912 feet; by La Condamine, at 56,749 toises; and by Ulloa, at 56,768 toises. The northern party found a place for their operations between Tornea in Lapland and the mountain of Kittis, 57′ 29.6" further north, in lat. 66° 48′ 22′′. The difference of latitude being determined, they measured a base line upon the frozen rivers, 2 measurements giving a difference of only about 4 inches. The arc being then determined, it was found to give 57,422 toises to the degree. With this result they returned to France, being absent only 16 months. The greater length of the degrees as they approach the poles was thus established, and consequently the greater equatorial than polar diameter of the earth. Multiplied measurements in different parts of the earth now became important to determine its true figure. They have been made in various countries, and confirm the general conclusions of Huyghens and Newton. La Caille's measurement at the cape of Good Hope in 1751, the only one in the southern hemisphere, presented anomalies, or showed great irregularity in the figure of the earth, which were not explained till, nearly a century afterward, the arc was remeasured with great care under the auspices of the British government, and it was shown that the discrepancy was owing principally to the deviation of the plumb

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line of La Caille by attraction of the mass of the by means of another the line was made to reach mountain near by. In North America the first Formentara, distant 12° 22' 13.39" from Dunmeasurement of this character was by Mason kirk, its northern extremity. The result of this and Dixon in 1764–5, on the peninsula between extension affected the quadrantal arc before Delaware and Chesapeake bays. The arc was obtained so little, that the standard unit, the measured throughout with wooden rods, and mètre

; equal to the T6.0pt.ooo of the quadrant, the degree in mean lat. 39° 12' was found to be would differ scarcely 730.007 of the value before 363,771 feet, or 68.896 English miles. It has given it. A singular anomaly was noticed upon never been supposed that this was a very ex- some portions of this arc, and the same was obact measurement, but its accuracy has not been served in the English surveys, that where these disproved. In 1784 measurements were com- portions were considered separately, the length menced larger than any ever before undertaken of the degrees appears to increase toward the for the purpose of accurately determining the equator. This is supposed to be owing to some difference of longitude between the observato- disturbing cause, as, possibly, inequalities in the ries at Paris and Greenwich. Instruments of density of the strata which affected the instrogreat size and improved construction were pre- ments in use upon them. The effect is to produce pared expressly for this work, and the base line a slight uncertainty in the exactness of the reof 27,404 feet upon Hounslow heath was meas- sult obtained, and in the calculated proportion ured once with wooden rods of 20 feet length, of the polar to the equatorial axis of the earth. and once with glass rods of the same length in The length of the quarter of the meridian was frames. The junction of the triangles on the found to be 5,130,740 toises. Of the other two sides was completed in 1788; but the oper- measurements which have been made of an arc ations on the English side were regarded only as of the meridian, the most important are those a portion of the full survey of the island to be conducted in Hindostan by Col. Everest, in conafterward carried out. Still more extensive sur- tinuation of the work commenced by Col. Lambveys were commenced in France in 1791, with ton in the early part of the present century; the object of obtaining the exact length of the and those by Struve and Tenner in Russia (the quadrant of the meridian, in order to make use latter commenced in 1817 and completed in of a definite part of this natural and permanent 1853). A small arc of 1° 35' was measured quantity as a standard for all linear measures. near Madras by Col. Lambton; and another was The pendulum vibrating seconds in some de- commenced from Punnæ in the southern extermined latitude had been proposed as a means tremity of the peninsula, in lat. 8° 9' 32.51", of furnishing an unchangeable measure, but it and extended to Damargida, lat. 18° 3' 15". was given up because of its dependence upon After Lambton's death in 1823, Col. Everest the element of time, the measure of which is carried the work on further north for some time. arbitrary, and its sexagesimal divisions are in- In 1832, after an interruption, it was resumed admissible as the foundation of a system of and continued till 1840, when it reached Kalidecimal measures. Local causes also, as the ana, lat. 29° 30' 48', thus including 21° 21' geological structure of the locality, affect the (1,477 m.). Every precaution was taken, and rate of its vibrations. The length of the quad- the most perfect instruments were provided, to rant of the meridian, not being liable to these insure the utmost accuracy; and notwithstandobjections, was adopted instead, and a new meas- ing the natural obstacles of the climate, the urement was carried out on the meridian of heat, rains, and thick atmosphere, the malaria Paris under the distinguished astronomers De- of the plains, and the impenetrability of the lambre and Mechain, and the work was not in- jungles, the results obtained from the bases of terrupted by the political disorganizations of verification indicate as great exactness as has the years 1792, 1793, and 1794. The line was been attained in the best European measureextended across France from Dunkirk to Barce- ments. The whole extent of the Russo-Scandilona, making an arc of about go, and every navian arc is from Ismail near the month of precaution was taken to insure the most per- the Danube, in lat. 45° 20', to Fugeloe ip Fin. fect accuracy in the measurements. The base mark, lat. 70° 40'. The portion extending N. line near Paris was more than 7 m. in length from Tornea (4° 49') was measured by the (6,075.9 toises), and another of verification of Swedish and Norwegian engineers. The ground 6,606.25 toises near the southern extremity of throughout the whole extent of the line is rethe arc differed by measurement less than a foot markably favorable for the execution of this in length from its extent calculated from the work, on account of its freedom from great irtriangles extending from the first base more regularities of surface; but in the southern part than 436 m, distant. Though this arc thus forests spreading over a level country have determined was sufficient for the purpose re- rendered it necessary to raise many temporary quired, the French astronomers in 1805, after elevated stations; and in the north the ese an interval of 3 years, began to carry the meas- traordinary refractions of that region have addurement still further south, Biot and Arago ed to the difficulties of the work. This arc, directing the work after the death of Mechain. and that of Hindostan, give the measure of a The island of Ivica in the Mediterranean was large portion of the quadrant of the meridian, connected with the system by a triangle, one leaving only the degrees between 29° 30' and side of which exceeded 100 m. in length; and 45° 20' unmeasured from lat. 8° 9' to 70° 40'.

The French arc, extending from lat. 38° 40′ to 51°, fills up a portion of this gap, and they all together afford abundant data for an exact computation of the curvature of the meridian; and this is rendered the more certain from the standards of length used in India and Russia having been directly compared. Other arcs have been measured by Bessel and Bayer in Prussia; Schumacher in Denmark; Gauss in Hanover; beside a few others of less import. The longest arc measured in the progress of the U. S. coast survey is one of 34°, extending from Nantucket to Mount Blue in Maine. Great confidence is felt in the accuracy of this measurement, from the extreme care with which the triangulation is conducted. The work is not yet quite completed. An arc of parallel will also be measured along the Mexican gulf. From the various measurements that have been already made, different values have been calculated for the ellipticity of the earth, or the proportions between the polar and equatorial diameters. Prof. Airy, before the completion of the recent surveys, found the ellipticity, and Bessel afterward made it. The French and Indian arcs give a smaller ellipticity, as, but the Russian, it is thought, will be about. The following statement presents the average of several of the measurements: Equatorial diameter, 41,843,330 feet, or 7,924.873 miles; polar diameter, 41,704,788 feet, or 7,898.634 miles; difference of diameters, or polar compression, 138,542 feet, or 26.239 miles; ratio of diameters, 302.026: 301,026; ellipticity, length of degree at equator, 362,732 feet; length of degree at lat. 45°, 364,543.5 feet. Profs. Airy and Bessel, calculating from different sets of measurements, obtained the following results:

1

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Equatorial diameter..
Polar diameter....
Polar compression...
Ratio of diameters.

Airy, miles.

Bessel.
7,925.604
7,899.114
26.478
26.471
299.33 to 298.383 299.15 to 298.10

7,925.648
7,899.170

city thus obtained is generally or 3, differ-
ent values being allowed for the rate of increase
in the density of the earth from the surface to-
ward the centre. Degrees of longitude might be
measured instead of latitude for determining the
figure of the earth; but the difficulty would be
in the precise estimation of differences of longi-
tude in the celestial arc. The close approach of
the earth in its general form to the figure of hy-
drostatic equilibrium forcibly suggests the prob-
ability of the particles which compose its mass
having been in condition to move freely toge-
ther under the influence of the centrifugal force
and their mutual attractions. The conditions
that now obtain upon the outer portion of the
earth in the mobility and transporting power of
its waters, which cover of its surface, may be
regarded as sufficient to give, in long periods of
time, the observed external form; but the indi-
cations afforded by the pendulum of regularly
increasing gravity from the equator toward the
poles, fand hence of symmetrical arrangement
of the layers throughout, imply the existence
of similar conditions during the entire period of
the construction of the earth. The form and
dimensions of the earth being obtained, calcula
tions respecting its density or weight may be
made by several distinct methods. The one first
applied was originally suggested by Bouguer-a
comparison of the attractive power of a moun-
tain of known dimensions and density with that
of the earth of known dimensions, whence its
density might be computed. Newton had al-
ready estimated that a hemispherical mountain
3 m. high and with a base of 6 m. diameter
would cause a plummet to be deflected 1' 18"
from the vertical. In making the trial the
plummet is attached to a delicate astronomical
instrument, with which observations are made
to determine the meridian altitudes of stars near
the mountain, and on the same parallel at a dis-
tance accurately determined and sufficiently far
off to be beyond its influence. The difference
in the 2 altitudes shows the power of attraction.
Observations are sometimes made from stations
on opposite sides of the mountain, and the re-
sult is then obtained by a different plan from
the above. Bouguer, in 1738, observed the in-
fluence of Chimborazo in deflecting the plummet,
and unsuccessfully endeavored to compute its
amount from observations made at 2 stations on
the S. side only. In 1772 Dr. Maskelyne pro-
posed to the royal society to try the experiment
upon some mountain in Great Britain; and the
society thereupon appointed a "committee of
attraction," including in it, with Maskelyne,
Cavendish, Franklin, and Horsley. Mr. Charles
Mason was intrusted with the selection of a
proper hill, and finally Schehallien in Perthshire,
Scotland, was fixed upon. The primary meas-
urements were made by Mason in 1774, to de-
termine the distance apart of the stations to be
used, one on the N. and the other on the S. side
of the hill, under similar slopes. By triangu-
lating, Dr. Maskelyne found this distance to be
4,364.4 feet, corresponding in that latitude to a

The ellipticity of the earth is always expressed by a larger fraction than the above when computed from observations upon the vibrations of the pendulum in different latitudes. It is variously given from 5 to 8 These observations have been made at so large a number of places, that the effects of local causes of irregularity would be expected to disappear; yet there is an unexplained discrepancy with the results of the geodetic method. This is perhaps owing in part to the variable resistance opposed by air of different densities, the effect of which can be obviated by conducting the experiments in a vacuum. The ellipticity has also been calculated from some irregularities in the motions of the moon, caused by the equatorial protuberance; and it may well be remarked as an extraordinary fact that from this source a strong confirmation should be afforded of the correctness of the results obtained from the measures of the meridional arcs. The ellipti

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