Page:Popular Science Monthly Volume 53.djvu/329

Rh been divided with reference to the origins of storms and also the paths of the storms. All the paths cross New England, and the chart shows what a harsh, changeable climate this section has. There is no other region on the face of the earth, not even excepting Siberia, where there are such sudden and violent changes of weather as in New England. All storms that visit the United States cross New England and pass off toward the St. Lawrence Gulf, if they do not die out on the way. Lows move on an average at the rate of twenty-five miles per hour.

We have now seen that highs and lows have definite points of origin or entrance into the country, and that they follow well-established tracks. It is clear, therefore, how their location a few hours in advance may be estimated.

Highs are not usually accompanied by rain, but the temperature falls in advance of them as they pass over the country. The lows, on the contrary, are the storms, and usually carry rain with them. The greatest rainfall is usually to the northeast of the center of the low, and the low tends to move toward the point where there is the heaviest rain. The temperature of the air rises in the regions to the east of the low, and falls to the west of it.

Having located the highs and lows that exist and determined what paths they are likely to follow, from the laws that have been



explained, it may be seen how the direction of the wind, the occurrence of rain, and the changes in temperature can be predicted (Fig. 5). fig. 5 is a reproduction of a newspaper weather map. The dotted lines connect all points having the same temperature, temperatures ten degrees apart being chosen. The full lines are lines of equal barometric pressure, there being a line for each one tenth of an inch difference in pressure. The arrows fly with the wind. Rain