ft. above the surface of the water. Upon the a thick forest.-The length of the Colorado, from the sources of Green river, is about 2,000 m. It is navigable for steamers to Callville, 612 m.; and it is thought that navigation may be carried to the foot of Grand cañon, 57 m. above. Arnold's point, 35 m. from the mouth, is the head of navigation at low water (winter) for vessels drawing 9 ft. To the head of tide water, 40 m., navigation is difficult and dangerous, from the rapid rise of the tide and the shifting of the channel. Above this point the current, obstructed by small snags and sawyers, runs from 1 to 3 m. an hour (in freshets from 2 to 6 m.) through a narrow channel. The rise of ordift.nary spring tides is 12 ft. In freshets the river rises at Arnold's point 15 ft. above low water, and in seasons of unusual height it flows back over the California desert, filling up several basins, and what is known as New river, in Lower California. This water remains one or two years, when it is swallowed up by the sands, or evaporated by the hot sun. At the mouth of the river a good harbor was discovered in 1864. It consists in fact of a second mouth of the Colorado, which branches off some 80 m. up, and empties in such a way as to afford secure shelter from the terrible "borers" of the gulf. It is from 50 to 80 yards broad, and with perpendicular banks of hard clay some 25 ft. high at low tide. At high tide the banks overflow a few inches, but the anchorage remains good. About 6 m. up there is an abrupt fall extending across the stream, some 4 or 5 ft. high at low water, but disappearing at high tide. The depth of water in this singular harbor at low tide is from 15 to 25 ft. This harbor is now used almost exclusively by the vessels in the Colorado trade. Their cargoes are here transferred to the small river boats and barges, and they here receive their outward-bound freights.-In 1540 Fernando Alarcon, in a voyage to explore the gulf of California, by order of the viceroy of Spain, discovered the mouth of the Colorado, which he describes as a very mighty river, which ran with so great a fury of stream, that we could hardly sail against it." He fitted out two boats with which he sailed up the river. Father Kino, about the year 1700, also sailed up to the confluence with the Gila, where he established a mission. Lieut. Ives explored the Colorado below the cañons in a steamer in 1857. The first descent through the cañons was made in 1867 by James White, from a point on Grand river about 30 m. above its junction with the Green. White, Capt. Baker, an old miner and an ex-officer of the confederacy, and Henry Strole were prospecting for gold in the W. portion of Colorado. Having met with il success, and having lost Capt. Baker during an attack by Indians in a lateral cañon of the Grand, which they had descended for water, White and Strole determined to attempt an escape by the river rather than retrace their steps through a country beset by Indians. They constructed a frail raft of a few pieces of drift wood, and, having secured their arms and provisions, commenced their downward journey on the night of Aug. 24. Subsequently the raft was generally secured by night and allowed to drift only during the day. On the 28th, while descending a cataract, Strole was drowned, and all the provisions were washed overboard. White continued the journey alone, amid great peril from cataracts, rocks, and whirlpools, hemmed in by the walls of the cañon, and 10 days after reached Callville, having tasted food but twice during that period. Once he obtained a few green pods and leaves from bushes growing along the stream, and the second time he was given some food by Yampais Indians who occupied a low alluvial strip of land along the river, the trail to which from the plateau was known only to themselves. In 1869 a corps fitted out by the United States government, under the command of Prof. J. W. Powell, started in boats from the upper Green river in Wyoming territory, and, after much peril and many hair-breadth escapes, reached Callville, having passed through the whole length of the cañons. In 1871 another expedition under Prof. Powell was fitted out for the exploration of the Colorado valley. The portion of the river embraced in this exploration is about 1,000 m. in length, commencing where the Union Pacific railroad crosses Green river, and extending down the stream to the end of the Grand cañon. E. and S. of the river the survey runs back from 10 to 40 m. from the stream. On Jan. 1, 1873, the exploration had been completed of the region N. and W. of the Colorado, drained by its tributaries, from the Rio Virgen on the south to the Dirty Devil on the north, embracing a territory 300 m. long and 175 m. wide. N. of this a general reconnoissance had also been made of the territory between the Wasatch mountains and San Pete valley on the west and Green river on the east, embracing the valley of the Uintah, the ranges of mountains and extensive plateaus lying S., the valley of Price river, the Wasatch plateau, the valley of the San Rafael, and the plateau and mountains in which this river has its sources. The survey of the region embraced in Prof. Powell's plan is to be completed in 1875, when the entire valley of the Colorado will have been explored, the portion above the Union Pacific railroad and that below the Grand cañon having been already surveyed. COLORADO, or Cobu Leubu, a river of the Argentine Republic, rising in the Andes about lat. 35° S., and flowing S. E. across the pampas through an imperfectly known country to the Atlantic, which it enters in lat. 39° 51' S., lon. 62° 4′ W.; length about 600 m. By some authorities it is supposed to receive the waters of the Mendoza and the Desaguadero, which drain the great system of lakes in San Luis and Mendoza. It discharges through several mouths, the principal one having two fathoms of water at low tide. It is obstructed seaward by shifting sand banks. The tide rises at its mouth from six to nine feet. It is said to be navigable only about 120 m. COLOR-BLINDNESS, a curious defect in vision, depending on a want of sensibility in the eye, or perceptive capacity in the brain, in consequence of which certain colors are not distinguished, or all colors are alike invisible as such. It is believed that attention was first called to this defect by the publication by Dr. Dalton, the distinguished chemist, in 1794, of the particulars of his own case. The name given to the affection is that proposed by Dr. George Wilson, from whose work on the subject (Edinburgh, 1855) the following summary is chiefly condensed. It has also been called Daltonism. A cause for the lateness of the discovery of this phenomenon may be found in the fact that while the ignorant would not investigate a disability of the kind under which they might labor, the educated and intelligent would learn to compensate for it by the use of other senses. No mention of color-blindness has been found in ancient or modern writers up to the period named; but the examples of the affection already collected are numerous, and among its subjects were Dugald Stewart and Sismondi, contemporaries of Dalton. The difficulty shows itself in three forms or degrees: 1, in an inability to distinguish nicer shades and hues, such as grays and neutral tints; 2, in inability to distinguish certain primary colors from each other, as red from green, or these from secondary or tertiary hues, as scarlet, purple, &c.; 3, in inability to discern any color as such, the person seeing only white and black, lights and shades. In the first degree, this affection is, among males, rather the rule than the exception. Dr. Wilson found that of 1,154 persons examined by him in Edinburgh, more than one in 18 were in a greater or less degree color-blind; and that of 60 persons in the chemical class of the Edinburgh veterinary college, the majority declined to name any colors beyond red, blue, yellow, green, and brown; while they failed entirely in attempting to arrange nearly related hues of yarns or stuffs, or those of varying shades of the same hue. He found that pink and other pale colors, especially pale yellow and blue and green, were often confounded. The same thing happened with orange and yellow, lilac and bluish gray, &c. In the second degree, in the less marked cases, red and green, or these with olive and brown, fail to be distinguished. And it is apparently singular that colors among the most distinct to a normal eye are in these cases the most easily confounded, red and green being more readily so than yellow and purple; while green is in these respects the most delinquent of all the colors. Dugald Stewart could not distinguish the red fruit of the Siberian crab from the green color of its leaves. Three brothers, Harris, mistook red for green, orange for grass green, yellow for light green. A tailor at Plymouth regarded the solar spectrum as consisting only of yellow and light blue; while indigo and Prussian blue he pronounced black. Dr. Dalton could not by daylight tell blue from pink; he scarcely saw the red of the spectrum, and considered the remainder of it as showing but two colors. But a failure to perceive the more refrangible rays is most common. Seebach concludes that all eyes, however imperfect otherwise, see yellow; and that the sensations of complementary colors are inseparable, so that if the eye be sensible or insensible to either it will be so to both, the eye that fails to see orange also mistaking blue, &c. In the third degree, however, admitted by other observers, all colors are recognized only as giving certain degrees of light or shade. This form is rare. Dr. Wilson found but one case; and in this some of the colors could be named by gas light or transmitted light, none by reflected daylight. The color-blind very often do not know their own defect; and in the lower walks of life their lack incapacitates them for certain employments, or may even imperil life. These evils particularly befall weavers, tailors, gardeners, railway attendants, sailors in the steam service, and others dependent on the use of colored articles or the perception of colored signals. The importance of a correct perception of colors, in the present modes of signalling upon railways and shipping, cannot be overestimated. For example, the English admiralty orders require at night a green light on the starboard, a red light on the port side of vessels; and by the color the steersman must know which side of the vessel is toward him, consequently whether it is going to right or left, and whether to starboard or port his helm. Although no case of accident has yet been traced to color-blindness in the attendants, yet such a result is easily conceivable, especially as their powers of vision are not tested; and the most doubtful complementaries, red and green, are much in use as signals. Practical inferences are that the ability in this respect of candidates for the posts of sailors and railway men should always be first carefully tested; but, better still, that form and position of signals should, as far as practicable, be substituted for color, as the former are qualities less liable to be mistaken, and the color-blind generally perceive form even more correctly than other persons.-The cause of color-blindness probably lies somewhere between the eye, as an organ, and the mind; or more correctly, in a want, partial or total, of a certain perceptive faculty, that of color, as an element of active mind. Dalton thought the retina or humors of his eyes must be colored, and probably blue; a nice post-mortem dissection of his eyes revealed no abnormal coloration or appearance whatever. Dr. Trinchinetti proposed as a cure the extraction of the crystalline lens; but Wilson gives a case of cataract, in which color-blindness supervened on the extraction of the lens. In one instance, the latter found the difficulty to follow permanently on concus sion of the brain; sometimes it was temporary, and dependent on congestion, dyspepsia, or hepatic derangement; most frequently it was congenital. Color-blindness is generally hereditary. Leber, who examined many cases, found it a frequent sympton of atrophy of the optic nerve, and of scotoma (musca volitantes, &c.). Dr. Argyll Robertson (Edinburgh "Medical Journal," February, 1869) found it accompanying a case of spinal disease. Dr. Chisholm of Charleston, S. C., observed it in a case of inflammation of the optic nerve. It is often, however, unaccompanied with any impairment of vision. It has been observed during pregnancy, and Lawson met with a case which was produced by over use of the eyes in sorting colors. As has already been noticed, the ethereal waves of light in the different colored rays vibrate in different times, the number of vibrations in the middle red ray being about 477,000,000,000,000, while the number in violet light is 699,000,000,000,000 times in a second. There are also waves on either side of these limits which are too slow on the one hand, and too rapid on the other, to be perceived by the human eye, just as some vibrations in the air may be too slow or too rapid to be perceived by the ear. That some persons can perceive a lower tone of red, or the more extreme rays of the violet spectrum, as well as that some can perceive lower or higher notes in music, is a matter of observation, as also the fact that the perception of the depth and tone of various colors varies in different individuals. It is then a matter of no great surprise that in some persons the retina should fail to perceive the difference between the vibrations which take place in some of the colored rays. In the congenital cases, and in some others, the attempt at cure by medicines has been found utterly hopeless; of a cure through education no case is established. The want may be alleviated by carrying about a chromatic scale, named, for purposes of comparison; but little help is thus derived. It is strange that the substitution of artificial for solar light seems as yet to offer decided relief in the largest number of cases; and a draper has been known to keep his shop lighted with gas during the day for this purpose, and with success. Very white light is less useful in these cases; the best being a light yellow by passing through glass stained with preparations of silver, uranium, or iron. Dr. Wilson found that a good test for persons confounding red and green, and who may be unaware of the fact, was obtained by placing before their eyes a red glass; the beholder is at once astonished at the difference which he discovers in looking at the two colors. COLORIMETER, an instrument for measuring the depth or color in a liquid by comparison with a standard liquid of the same tint. The comparison is made either by varying the depth of the stratum of liquid under examination till it exhibits the same intensity of color as the normal liquid, and then measuring the depth of the stratum, or by diluting the stronger-colored liquid with water till equal columns of the two exhibit the same color. COLOSSE, an important ancient city of S. W. Phrygia, on the river Lycus, an affluent of the Mæander. Xenophon speaks of it as being a large and flourishing place at the close of the 5th century B. C. At a still earlier period (481) Xerxes passed through it on his way to Greece. Colossa was famous for beautifully dyed wool, and carried on an extensive trade in that article. After the time of Cyrus the Younger it seems gradually to have fallen into decay. It was the seat of one of the earliest Christian churches, to which one of St. Paul's epistles is addressed. During the middle ages it was called Chonæ. Khonos, a modern town on its site, is 120 m. S. E. of Smyrna. ing near the centre of the ancient city, upon the spot once occupied by the reservoir of Nero, about 500 yards S. E. of the Roman forum, and 200 S. W. of the baths of Titus. Its ruins are still sufficiently complete to show the form of almost the entire structure, and are among the best preserved and most magnificent remains in modern Rome. The building was at first called the Flavian amphitheatre, the name Colosseum being first used some centuries later with reference to its immense size. It was begun by Vespasian, built by him as far as the top of the third row of arches, and finished by his son Titus, by whom it was dedicated in A. D. 80, with games, gladiatorial shows, and scenic exhibitions of unprecedented splendor, a great number of gladiators and several thousand wild beasts being killed in contests in COLOSSEUM, Coliseum, or Coliseum, an im- the arena. The building, which covers nearly mense amphitheatre in Rome, the largest per- five acres, and in its complete state had acmanent structure of the kind ever built, stand-commodation for 80,000 spectators, is in the form of an ellipse; its longer diameter is 615 ft., its shorter 510; the height of its outer wall, where it is still entire, is 164 ft. The arena within is 281 ft. in length and 176 in breadth. The exterior wall of the edifice consists of four stories, of three different orders of architecture; the first (lowest) is Doric, the second Ionic, the third and fourth Corinthian. The material was chiefly travertine for the principal walls, the spaces between being filled in with brick. The part of the Colosseum designed for spectators is in its leading features arranged like that in other ancient structures of the same design (see AMPHITHEATRE); but the fact that in the ruin no traces are to be found indicating that the ranges of seats ever rose higher than at present, i. e., to the bottom of the third story, or half the whole height, has perplexed all antiquaries. It is hardly to be supposed that the whole upper part of the building, erected at immense expense, was added for no object but to increase the exterior height; yet, if the places for spectators never extended to a higher point than would appear from the remains now existing, the upper stories would seem to have been only useful for that purpose. Various theories have been advanced on this subject; one of the most plausible is that the extra stories were in some way rendered necessary by the machinery of the velarium (awning or temporary roof) sometimes spread over the whole; another, that narrow galleries ran round the inner circumference of these upper walls; but this must remain a matter of conjecture. What was the position of the dens for the wild beasts used in the combats of the arena has been another vexed question, as no traces of them are found; it appears probable, however, that they were situated under the podium, where they would open directly into the arena.-The best known events in the history of the Colosseum are those connected with the history of the Christian church. Many of the early Christians suffered martyrdom in its arena. St. Ignatius is said to have been the first, he having been given to the lions in this amphitheatre in the earliest days of Christianity. St. Potitus, St. Prisca, St. Martina, and many others, are recorded as having been put to death in the Colosseum in the 2d and 3d centuries, with hundreds of unnamed martyrs, of whom the only records remaining are notes of the number suffering together on the occasion of one festival or another. A cross now stands in the centre of the arena, erected in memory of their martyrdom; and around the edge, close to the wall of the podium, are small chapels or stations, marking the stages of the Via Crucis, the devotional exercise of the Roman Catholic church commemorative of Christ's progress to the crucifixion. These devotions are still performed in the Colosseum on Friday of each week. Excepting the record of these martyrdoms, carefully compiled by ecclesiastical historians and undoubtedly largely mixed with tradition, the Colosseum finds singularly little mention in the works of ancient authors. The building is supposed to have remained entire until Rome was invaded by Robert Guiscard, who began its demolition to prevent its being used as a fortress. It served that purpose in the middle ages, however, and was long held as a stronghold by the family of Frangipani, until they were dislodged by their enemies the Annibaldi. In 1312 the muncipality took possession of it, and it was again used for public entertainments, especially for bull fights. In 1387 the canons of the Lateran were allowed to use it for a hospital. After the 14th century it began to be despoiled by the great Roman families, who used its stone to build their palaces. In the time of Sixtus V. it was proposed to turn it into a place of trade, erecting shops under the arcades; but the plan was unsuccessful. Clement XI. endeavored to erect within it a manufactory of saltpetre, but he failed to carry out his design, and was persuaded to finally consecrate it to the memory of the martyrs, thus throwing over it a protection which preserved it from further injury. COLOSSIANS, Epistle to the, one of the smaller Pauline epistles of the New Testament, addressed to the church of Colossa. It bears a great similarity to the Epistle to the Ephesians, and is directed against some heretical doctrines which had crept into the Colossian church, and which this epistle represents as endangering the purity of the Christian religion. In the opinion of former exegetical writers these heretical doctrines were the views of Judaistic theoVOL. V.-8 sophists, or of some pagan philosophical system; Credner and Thiersch believed a kind of Christian Essenism to be referred to; but the prevailing opinion now is that we find here early traces of Gnosticism. The Pauline origin of the epistle was generally recognized until Mayerhoff (Der Brief an die Kolosser, Berlin, 1838) denied its authenticity. He was followed by Schwegler (Das nachapostolische Zeitalter, Tübingen, 1845-'6), and by F. C. Baur (Paulus, der Apostel Jesu Christi, Stuttgart, 1845). Ewald (Die Sendschreiben des Apostels Paulus, Göttingen, 1857) expressed the opinion that the epistle was written by Timothy after receiving from Paul special instructions with regard to the contents. But the great majority of exegetical writers adhere to the tradition of the Pauline origin of the epistle. According to David Schulz (1829), with whom several other modern writers (as Schenkel) agree, the epistle was written during the captivity of Paul at Cæsarea, in 60 or 61; but the almost universal testimony of tradition, according to which it was written by Paul from Rome in 62, is ably defended by Bleek (Vorlesungen. über die Briefe an die Kolosser, &c., Berlin, 1865) and others. COLOSSUS (Gr. κoλoσσóг), a statue of gigantic size. Such statues were often erected in ancient times, and many still remain in existence, especially among the ruins of Thebes in Egypt. The most celebrated colossus of ancient or modern time was that at Rhodes. This city had been besieged by Demetrius Poliorcetes, king of Macedon; but, assisted by Ptolemy Soter, king of Egypt, the citizens repulsed their enemies. To express their gratitude to their noble friends, and to their tutelary deity, they erected a brazen statue to Apollo. Chares of Lindus, the pupil of Lysippus, commenced the work; but having expended the whole amount intrusted to him before it was half completed, he committed suicide, and it was finished by Laches. The statue was 105 ft. high, and hollow, with a winding staircase that ascended to the head. After standing 56 years, it was overthrown by an earthquake in 224 B. C., and lay nine centuries on the ground, and then was sold to a Jew by the Saracens, who had captured Rhodes, after the middle of the 7th century. It is said to have required 900 camels to remove the metal, and from this statement it has been calculated that its weight was 720,000 lbs. According to Pliny, Rhodes had 100 colossi of inferior size. The researches of Cesnola in Cyprus have discovered many colossi in that island. Phidias erected several colossi. His Minerva in the Parthenon was 39 ft. high, composed of gold and ivory. Upon the shield was sculptured the battle of the Athenians and Amazons; on the buskins the battle of the centaurs and Lapithe; on the pedestal, the birth and history of Pandora. He likewise erected for the Eleans a statue of Jupiter 60 ft. high. Lysippus, in the time of Alexander the Great, constructed |