Observation, Army of

An army confined to checking the advance of a hostile force and observing its movements is an army of observation; while an army occupying an enemy's country and establishing itself there for a time is an army of occupation; e.g., Scott's army in Mexico, after the capture of the City of Mexico, and the German army in France after the capitulation of Paris. institution corresponding to a modern observatory which existed before the Christian era was that founded at Alexandria by Ptolemy Soter ab. 300 B. C. Observation and investigation were carried on here for ab. 400 years. It was made famous by the work of Claudius Ptolemy and many others of le er note. During the middle ages observatories were founded at Bagdad in the 9th century, at Mokattam near Cairo ab. 1000, at Merágha in Persia ab. 1260, and at Sam ark and in 15th century. At these places observations were carried on with instruments made after the fashion of those used at Alexandria 1,000 years earlier, and, if no great advance was made, the science was at least preserved from extinction. Among the early observatories of Europe the most famous were those of Bernard Walther at Nuremberg 1472, Tycho Brahe on the Danish island of Huen (1576-97), Landgrave William III. at Ca el (1561-97), and Hevelius at Dantzic, 17th century. More recently the number of observatories, both public and private, has become very great. G. H. Boehmer in the Smithsonian report for 1886 gives a list not profe ing to be complete of 76 American and 265 foreign observatories. The following are some of the more prominent, with names of directors, astronomical position, and most important instruments.