PRINCIPE                                                   1549                                                 PRINTING

university consists of the academic and graduate departments and of John C. Green School of Science, the last including departments of science, civil engineering and electrical engineering. Bachelor's, master's and doctor's degrees are conferred. There are 13 fellowships and 113 scholarships The faculty numbers 174, the students 1,442 and the library 278,000 volumes. The productive funds amount to $3,702,600 and the income to $1,316,984. Princeton Theological Seminary (Presbyterian), founded in 1812, has 16 instructors, 163 students and a library of 72,000 volumes. With the seminary is associated the fame of The Princeton Review, (1825-72), edited by Charles F. Hodge.

Principe or Prince's Island is a Portuguese possession in the Bight of Biafra, due east of French Kongo. It forms an independent colony with Säo Thome (q. v.). Its population is 4,327.

Print'ing is the art of producing impressions from characters and figures on paper or any other substance, but in this article it is confined to the art of making impressions with movable types, which may justly be esteemed among the greatest of human inventions. Notwithstanding the importance of this invention, it is not certain to whom the credit belongs, as it is contested by the Hollanders in favor of Laurens Cóster (1423) and by the Germans in favor of Johann Gutenberg (1438). The most general opinion would seem to be in favor of Gutenberg, but it is not impossible that both made the invention about the same time, during the first half of the 15th century. Between 1450 and 1455 Gutenberg printed a Bible, copies of which are still in existence although exceedingly rare and valuable; and, besides this Bible, some other specimens of work from his press at Mayence (Mainz) have been discovered. The Dutch at Haarlem preserve and show similar specimens of early printing by Coster. Mayence, Haarlem and Strassburg certainly were the places where printing was done before the art extended to Rome, Venice, Florence and other European cities. The art was introduced into England in 1474 by William Cax-ton, who set up a press by Westminster Abbey. The first printing-press in the United States was set up in the house of the president of Harvard College at Cambridge, Mass., in 1639, and in 1674 another was established in Boston, after which other presses were gradually introduced throughout the colonies. Until the beginning of the 17 th century the press used was a screw-press, with a contrivance for running the form of types under the point of pressure; force having been thus applied, the screw was relaxed and the form withdrawn, with the impression executed on the paper. The defects of this press were at length partially remedied by William Jansen Blaen of Amsterdam, who invented a press in which the

carriage holding the form was wound below the point of pressure, which was given by moving a handle attached to a screw, hanging in a beam having a spring, which caused the screw to fly back as soon as the impression was made. This kind of press, which was mostly of wood, continued to be used until the beginning of the 19th century. The first improvement on this press was made by the celebrated Earl of Stanhope, who constructed a press of iron and applied such a combined action of levers to the screw as to secure easier and more efficient working. Numerous improvements succeeded, the screw being dispensed with, and the pressure being effected by levers. The chief among these was the Columbian press, invented by George Clymer of Philadelphia in 1818.

Meantime, in 1811, Frederick König, a German printer, had invented a press in which the impression was given by a cylinder, the inking being done by rollers and the paper being carried through the machinery on tapes. John Walter of the London Times was so favorably impressed with this method of printing that he engaged König to make a double cylinder-press which should print two copies of a form at each revolution of the cylinder, but only on one side of the sheet. This press, which was completed in 1814, made about 1,800 impressions an hour, and was the first printing-press in the world operated by steam. A few years later König invented an improvement on this press, in which the sheet, after an impression had been made on one side by one of the cylinders, was turned over to receive an impression on the other side by another cylinder; but the march of improvement did not stop here. The circulation of newspapers increased to such an extent that in 1855 Richard M. Hoe of New York brought out the rotary printing-press, in which the pages of type were placed on a horizontal cylinder revolving on its axis, against which the sheets were pressed by a number of smaller cylinders, which were so arranged in a framework as to require a feeder for each one of these smaller cylin ers. Such a press with six cylinder", each making 2,000 impressions an hour, could turn out 12,000 sheets, printed on one ..ide, in an hour, and those with eight nd ten cylinders in p.oportion. But the H >e machine, with -11 its advantages, printed only one side at a tit e, and between ii 63 and 1868 the V\ altei press was devised, by w. 'ch printi: g is done from a continuous roll of paper, which is printed on both sides from stereotype plates, cut in separate sheets and p ted. This press, when first introduced, :rinted from 12,000 to 15,000 sheets per h ur; but since that time many other web-printing presses have been introduced, by which sheets of four pages are printed at the rate of 50,000 or more an hour. By the introduction of steam-presses the trade of the printer has