SIGNALS 35 traced upon the charts from report to report, and the direction and rate of their progress together with their intensity be noted in time to give warning of their approach. Floods occurring upon the western rivers can be traced sometimes from the fall of rain with- in the respective watersheds, and along the courses of the different confluent streams, un- til culminating in the dangerous flood of the )rincipal river. In nearly the same manner
- hat storms can be traced upon the charts,
ipproaching changes of temperature and rain- " 11 are foreseen, and notice is frequently given time to prevent injury to agricultural and ler interests. In the analyses of the official luctions of the office, or the "probabili- ies," the percentage of verifications is found o have been as follows: 1872, 76'8 per cent. ; L873, 77-6 per cent. ; 1874, 84'4 per cent. The itionary signal is a red flag with a black itre by day, and a red light by night. This signal indicates a probability of stormy or dan- gerous weather for the port or place at which it is displayed, or in that vicinity. "While storms of limited extent, such as squalls, ter- loes, &c., may spring up suddenly or pass stween stations in such a way that their >ming or courses cannot be foreseen, exten- sive and well defined disturbances can as a lie be readily traced in time to forewarn the >asts or districts threatened. Arrangements ive been made with the chiefs of meteoro- ^ical services in Europe, in accordance with le recommendation of the Vienna conference )f meteorologists (1873), providing for the ex- mge daily of one report taken at the same istant over all the territories of the United ites, nearly all Europe, extending through iussian Asia to the Pacific coast, and in the ior.th.ern portion of Africa. These exchanges e made every 15 days by mail. Besides the lily bulletins and weather maps, the signal See publishes a weekly review of the weather rhich is furnished to the press, and a monthly 3view, accompanied with charts showing the )baric and isothermal lines, the prevailing (vinds, the tracks of low barometer, and a pre- ipitation chart for the month. SIGNALS, Fog. See LIGHTHOUSE, vol. x., p. SIGNALS, Naval. Naval signals are frequently lentioned by the classical writers, and recent ivestigation has discovered the fact that the Astern which prevailed during the naval su- premacy of Greece and Carthage bore a stri- king resemblance to our present army code, invented by Gen. A. J. Myer, U. S. A. Sig- nal flags began to be used in the English navy in the time of Elizabeth, or perhaps a little earlier. In the reign of James II. their use was somewhat systematized, and in 1790 or thereabouts, under Earl Howe and Kempen- felt, a regular code of day and night signals was perfected. Besides flags during the last century, arbitrary signs were used as signals, which were well known to all seafaring peo- ple. The signal to unmoor ship, for example, was the loosing of the maintopsail ; that to prepare for sailing was loosing the foretopsail and firing one gun. In general there are three classes of signals : those for the day, made by square flags and triangular pennants variously colored of red, blue, white, and yellow ; night signals, made with colored lights, rockets, &c. ; and fog signals made by steam whistles, fog horDs, bells, or guns. By means of the "In- ternational Code of Signals for the use of all Nations," all maritime countries use the same kind of signal flags, and having the signal book of each country printed in its own lan- guage, ships of different nationalities commu- nicate as readily with each other as ships sail- ing under the same flag. In most systems the signal flags represent the numerals from 1 to 10, and in the signal book, corresponding to the numbers from 1 up to several thousand, are words and phrases most likely to be used by ships. But in the code just referred to the consonants of the alphabet were used in pref- erence to numerals, by which means it was found that with 18 flags more than 78,000 dis- tinct signals could be made without displaying more than four flags at a time. The number of flags and their position are also significant. Thus, when but two flags are shown, " danger " or " urgency " is implied. If in a signal con- sisting of two flags a burgee (a swallow-tail flag) is uppermost, it is known at once to be an " attention " signal. If a pennant is upper- most, it is a compass signal. A square flag above indicates an "urgent" signal. JChree flags in one hoist express "latitude, longitude, time," and all ordinary signals required for communications. Four flags indicate geograph- ical signals. The flags representing the alpha- bet are for spelling out words not found in the vocabulary. With a pennant above, the name of a ship of war is indicated ; with a square flag uppermost, that of a merchant vessel. Observing, then, the colors of each flag, we seek in the signal book the same combination of letters and the corresponding message. Let us suppose, for example, that on the meeting of two ships at sea one is observed to hoist two flags. We know at once, it is an urgent signal, and on closer examination find the up- per one divided vertically, in white and red, the lower one a red burgee. The upper flag represents the letter H, the lower one the let- ter B. The combination H B in the signal book stands opposite the sentence, " Want im- mediate assistance." Thereupon the second ship hoists a white and red vertical flag (H), and beneath a red pennant with white ball in centre (F). H F in the signal book corresponds to the sentence, " We are coming to your as- sistance." As each ship has a signal book printed in the language of its country, this code furnishes a kind of universal language. If the ship first mentioned had found herself on a strange coast, she might have made the same signal to a shore station, and received
