NATIONAL PARKS 383 NATURAL BRIDGES observatory on Capitol Hill in this year, and the Secretary of the Navy directed the purchase of necessary instruments for observations in meteorology, and as- tronomy. The results accomplished at the observatory were published in 1846, the first American work of its kind. Con- gress authorized the erection of a Na- tional observatory in 1842, and under Lieutenant M. F. Maury a special study was made of ocean currents, and hydrog- raphy. Recording observations by electricity was begun in 1849. Professor Asaph Hall in 1877 discovered satellites of Mars through Alvan Clark's 26-inch lens tele- scope, the largest made up to that time. In 1893 th-e observatory was moved to Georgetown Heights. Since 1893 the ob- servatory has co-operated with other na- tions in astronomical work. In 1913- 1914 the observatory, acting with the French, made the first direct determina- tion of the difference of longitude be- tween Washington and Europe by ex- change of radio cigns from Arling:ton and the Eiffel Tower station, Paris, The National Observatory has published 50 volumes descriptive of its work. NATIONAL parks: AND RESER- VATIONS, certain public lands of the United States which have been reserved from settlement, and are retained and improved by the United States Govern- ment as National parks. Their location and area in 1920 were as follows: National Parks Area in in Order of Location Sq. Miles Creation Hot Springs, Middle Arkansas 1% 1832 Yellowstone, Northwest. Wyoming.. 3, 348 1872 Sequoia, Middle E. California.. 252 1890 Yosemite, Middle E. California. .1,125 1890 Oeneral Grant, Middle E. California.. 4 1890 Mount Rainier, West c'tr'l Wash'ton.. 324 1899 Crater Lake, Southwestern Oregon.. 249 1902 Wind Cave, South Dakota 17 1903 Piatt. South Oklahoma 1% 1904 SullysHill, North Dakota IV^ 1904 Mesa Verde, Southw'st'n Colorado... 77 1906 Clacier, Northw'st'n Montana. .1,534 1910 Rocky Mountain, N. middle Colorado... 398 1915 ■Hawaii, Hawaiian Islands 118 1916 Lassen Volcanic, Northern California... 124 1916 Mount McKinley, South central Alaska. .2,200 1917 Grand Canyon, North central Arizona.. 958 1919 Lafayette, Maine Coast 8 1»19 NATIONAL PORTRAIT GALLERY, founded in 1856, was established at South Kensington, in 1869, but removed on loan to the Bethnal Green Museum in 1885. In 1891, when the collection com- prised nearly 900 portraits, a building for its special use was in progress at the rear of the National Gallery. NATIONAL SECURITY LEAGUE, an organization founded in 1914 by citi- zens of the United States who believed that the World War showed the nec- essity for greater armament on the part of the United States. While not com- mitting itself to any particular plan of National defense, the League favored a much larger army and navy and used its effective organization to bring pressure upon Congress to grant the necessary appropriations. It enlisted members from all parts of the United States, and engaged in a publicity campaign to make known to the voters the need of "Pre- paredness." During the war the league used its organization in aiding the draft and in other work of assistance to the Government. NATIONAL SOLDIERS' HOMES. See Soldiers' Homes. NATIONAL UNION, American fra- ternal organization, incorporated in 1881, under the laws of Ohio, with headquar- ters in Toledo, O. In 1920 there were over 700 local councils organized, with a total membership of over 60,000. Insurance policies amounting to over $150,000,000 are carried by the members, and over $45,000,000 has been paid out in death benefits since the order was established. NATUNA ISLANDS, three groups of islands extending from the W. coast of Borneo a great way to the N. W. The largest. Great Natuna, is about 30 miles long N. to S., and 20 miles broad E. to W. They are densely wooded. NATURAL BRIDGES, tunnels eaten through rocks by streams, etc. There are 10 of these natural curiosities, many of them of great beauty, in various parts of the United States; that of Virginia being the most celebrated. The arch of this one is 60 feet spring, depth 200 feet, crown 40 feet thick. In Walker co., Ala., is a natural bridge in which the stone is so stratified as to resemble masonry. In Trinity co., Cal., a small river runs for 3,000 feet through an arch of 80 feet span and 20 feet high. In Adams, Berk- shire CO., Mass., the Hudson Brook flows for 30 rods under an arch of white mar- ble. At the village of Natural Bridge, N. Y., Indian river flows through a se- ries of arches.
