_West India hurricanes_ occasionally visit the United States, especially in the late summer and early autumn. These storms begin as violent cyclones of small extent (300 to 600 miles in diameter), usually somewhere east of the West Indies, sweep in a long curve across the Caribbean Sea, and then turn north, either passing up along the Atlantic Coast or crossing the Gulf of Mexico into the southern United States. Soon after entering the temperate zone they increase in size and diminish in violence, but are still vigorous enough on reaching the Gulf or South Atlantic Coast to cause great devastation. Low-lying shores are often inundated by the immense waves they generate. _Cold waves_ are the rapid and severe falls in temperature that sometimes occur in winter, especially at the front of an anticyclone. Warnings of these occurrences, issued by the Weather Bureau twenty-four to thirty-six hours in advance, often result in the saving of millions of dollars' worth of merchandise susceptible to damage by freezing. _Frosts_ in the spring and autumn are also predicted with great success, to the immense advantage of farmers, market-gardeners, and horticulturists. The practice of smudging or heating orchards, now so widespread, is usually carried on under the advice of the Weather Bureau, which gives prompt notice to the orchardist when such precautions are in order. The bureau publishes charts showing the average and extreme dates of the last frost in spring and the first frost in autumn for all parts of the country. [Illustration: LOOKING DOWN ON A SEA OF FOG FROM MT. TAMALPAIS, CALIFORNIA] A _fog_ is a cloud resting on the surface of the earth. In the United States fog is commonest along the northern and middle parts of the Atlantic and Pacific Coasts. In the interior of the country, especially the western part, it is of rare occurrence, the average number of days a year with fog being less than ten. Lastly--weather fallacies are rife. _Indian summer_ is merely a type of mild, hazy, heavenly weather that prevails intermittently during our long American autumns. The _equinoctial storm_ is a myth; the climate has not "changed" anywhere within the span of a human lifetime (one year differs from another, but there is no progressive or permanent change); and the _moon_ has nothing whatever to do with THE WEATHER. SUPPLEMENTARY READING CLIMATE AND WEATHER _By H. N. Dickson_ AMERICAN WEATHER _By A. W. Greely_ WEATHER SCIENCE _By R. G. K. Lempfert_ SOME FACTS ABOUT THE WEATHER _By W. Marriott_ Second edition. METEOROLOGY _By W. I. Milham_ The latest general textbook on the subject in English. FORECASTING WEATHER _By W. N. Shaw_ ELEMENTARY METEOROLOGY _By F. Waldo_