YELLOW SEA 475 YEMEN consisting of twelve medical men and a sanitary engineer, with Surgeon-Greneral Woodworth as president, was appointed by the Health Committees of the Senate and House of Representatives of the Congress of the United States to investi- gate the yellow fever epidemic, and they came to the following conclusions: (1) Yellow fever is a specific disease, due to a specific poison which has not been chemically or microscopically demon- strated, nor in any way made evident to the human senses; it is material and particulate, and endowed with the vital properties of growth and reproduction; the disease is not malarial, and malarial influences do not contribute toward its dissemination or moi'tality to any greater extent than to other epidemic diseases; a concurrence of local conditions seems to be necessary to the evolution of the disease, but what these are we have no positive knowledge. (2) Yellow fever is a disease of singular local attachments, often prevailing in a very small section of a city, with remarkable indifference to topographical and social surround- ings; while atmospheric air is the usual medium by which it is conveyed, it has been in no instance established that the disease has been carried to any consider- able distance by atmospheric currents, or by any modes or vehicles of conveyance other than those connected with human traffic and travel; the period of incuba- tion varies from two to five days; the fever is unknown in Asia; the white race is most susceptible to its in- fluence, and furnishes the highest ratio of deaths. YELLOW SEA (Chinese, Whang Hai), an arm of the Pacific Ocean; on the N. E. coast of China; length about 620 miles; greatest breadth, about 400 miles. It is very shallow, and obtains its name from the lemon-yellow color of its water near the land, caused by mud suspended in the water from the inflow of the Hoang-ho and Yangtse-kiang rivers. YELLOWSTONE, a river of the United States, which rises in the Rocky Mountains, about lat. 44° N. and Ion. 110° W. After a course of about 25 miles it passes through the lake of the same name, and runs N. through the Yellowstone National Park. Soon after issuing from the lake the river makes at intervals a series of falls (the last being 300 feet high), and traverses carions, one of which, the Great Caiion, is 30 miles in length, its steep sides being colored in bright hues and shaped in great variety of fantastic forms. Run- ning in a N. E. direction the river ulti- mately joins the Missouri about lat. 48° N., after a course of about 1,100 miles. Steamers can ascend it for 300 miles to the mouth of the Big Horn, which is its largest affluent. YELLOWSTONE LAKE, formerly called Sublette's Lake, a beautiful lake in Wyoming, at the N. E. base of the Rocky Mountains; in the National Park of the Yellowstone, at an elevation of 7,788 feet above sea-level. Its greatest extent is about 20 miles, and its greatest depth 300 feet. Its outlet is the Yellow- stone river, which issues from the N. end of the lake. The Upper Yellowstone river enters at the opposite side. This lake is surrounded on several sides by high mountains, among which are Mount Sheridan and Mount Langford. YELLOWSTONE NATIONAL PARK, a remarkable region in the extreme N. W. corner of Wyoming; set apart by Congress for a National reservation in 1872. Its area was originally 3,575 square miles, to which Congress, in 1891, added a tract of nearly 2,000 square miles to the S. and E. — nearly all more than 6,000 feet above sea-level, and ris- ing in the snow-covered mountains to 10,000 to 14,000 feet. Situated on the "Great Divide," its pine-clad mountains form the gathering ground for the head- waters of large rivers flowing away to the Atlantic and Pacific Oceans, and for the sake of the rainfall and the rivers its forests are carefully preserved. The mammoth hot springs are of a class with those in the geyser basin. The element of beauty enters into the forma- tions from the deposits left by the water. These have been built up by ages of activity, and are in scalloped terraces. Their greatest activity is manifested at the base of Capitol Hill, on the pictures- que bank of the Gardiner river. But there are unmistakable evidences of their activity for miles back, for cedar- crowned mounds yet yield treasures to the tourist who seeks specimens with a well-directed spade. In walking over some of the terraces where the water has ceased to run, the formation sounds hollow underneath, the action of the elements having built the terraces at the expense of the limestone beds below the surface. (javerns have been found underneath the now inactive basins, which are resplendent with stalactite and stalagmite formations that glisten under the blaze of a torch with singular bril- liancy. YEMEN ("the land to the right of Mecca"), a district in the S. W. of Ara- bia, bounded on the N. by Hedjas and on the E. by Hadramaut, and measuring about 400 miles in length by about 150
