198 Forecasting Weather. 



articles (the latter not always of a very profound or reliable 

 character), the attention of the public is frequently drawn to a 

 subject of every-day concern, so that even the man in the street 

 has begun to show an intelligent appreciation of the workings 

 of the thermometer, the rain-gauge and the sunshine recorder. 

 In spite of all such efforts there are, how^ever, myriads of people 

 who have no conception of the rules upon which the daily 

 weather forecasts are based, and it is to be feared not a few 

 who imagine that there is some connection between the opera- 

 tions of the prophet and the spinning of a coin. Any one who 

 will take the trouble to read but a few chapters of Dr. Shaw's 

 book will at once see that, in spite of failures, due to serious 

 limitations in the existing knowledge of the subject, the official 

 weather forecaster proceeds upon strictly scientific grounds, and 

 that the infinite variations in the weather are regulated l)y law 

 in very much the same way as any of the other ordinary 

 operations in nature. 



Without a chart the forecaster would be more helpless even 

 than the mariner ; and the opening chapter of Dr. Shaw's book 

 is therefore devoted largely to a description of the synoptic 

 weather chart, and the methods by which it is prepared. Every 

 morning reports of the state of the weather are received at the 

 Meteorological Office by telegraph from 29 stations in the British 

 Islands, 31 on the Continent, and 7 in the Atlantic islands of 

 Iceland, the Faeroe, the Azores, and Madeira. As soon as each 

 report arrives the reading of the barometer and thermometer 

 and the state of the wind and weather are inserted in proper 

 geographical position on a blank outline map. When the map 

 is fairly complete lines are drawn connecting all places or 

 positions in which the barometer stands at the same level, and, 

 as a result, the forecaster sees at a glance in which locality the 

 barometer is high, and in which regions it is low, the other 

 observations showing the weather conditions which prevail in 

 the neighbourhood of the various systems of high and low 

 pressure. After comparing one weather map with another, say 

 for the previous morning or evening, the problem which lies 

 before the forecaster is to form a mental picture of the chart as 

 it is likely to appear at the close of another twenty-four hours — 

 or in other words i^^ decide as to the nature of the changes 

 which will take place in the conditions of barometer, wind, and 

 weather. Bad weather is always associated with what are 

 known variously as cyclones, depressions, or areas of low baro- 

 metrical pressure. Fine weather of anything like a prolonged 

 character is due to the presence (if anti-cyclones or areas of 

 high barometrical pressure. The opposing systems are usually 

 in motion, those of the former class moving with more or less 

 swiftness, the latter far more slowly, and remaining in fact not 



