days, centering over Miami during the early morning of September 18.
Mr. Gray describes it as "probably the most destructive storm in the history of the United States, in so far as property loss is concerned, and the depression of the barometer at Miami was the greatest ever recorded in any storm in the United States."
The importance of the barometer long has been recognized by seamen but it is possible that many landsmen still do not appreciate its invaluable service in forecasting the approach and proximity of storms. Even the amateur yachtsman knows better than to venture into open water when the mercury in his barometer is depressed. During the recent hurricane the oscillations of the mercury were so great that Mr. Gray found it almost impossible to adjust the vernier, which is an attachment by which infinitesimal readings are recorded. Here it may be interesting to indicate the difference between the mercurial and the aneroid barometer, because of references which appear in the official account, and for the further reason that interest in the significance of the barometer is increased because the pressure was lower in this storm than ever before has been recorded by the Weather Bureau in the United States.
The mercurial barometer was invented by Torricelli in Florence, 1643. It consists of a straight glass tube hermetically sealed at one end, filled with mercury and set in a small basin of the same fluid, the column of mercury having equal weight with the mean pressure of the atmosphere on an area equal to the base of the column. Fluctuations are indicated by inches and decimals; for smaller divisions a vernier is used. The aneroid barometer, a cylindrical affair, is the invention of a Frenchman, M. Vidi, and records atmospheric pressure by a finely fashioned mechanical combination which traces variations upon a chart known as a barograph. The width of the chart ordinarily is sufficient for the inked needle to trace its record across the sheet, zig-zagging up and down as fluctuations are received by the highly sensitized cylinders, and simultaneously transmitted to the needle, but during the early morning of September 18 the needle dipped as far down as it could go and then went clear off the sheet. Not only was it the lowest pressure ever recorded by any barometer in the United States, but it was so much lower than the previous lowest record that Mr. Gray, recognizing its significance, got such a hair raising thrill as seldom comes to any man, for he knew that the storm which was hurling roofs and smashing buildings outside was
