358 THE POPULAR SCIENCE MONTHLY. 



during the most interesting period ; i. e., from 8 a. m., on the 3d of Oc- 

 tober, to 2 p. M, of the 4th. Previous to one o'clock on the morning of 

 the 4th but three observations are recorded : at 7 a. m., at 2 p. m., and 

 at 10 p. M. These indicate a steady decline in the barometer, and it 

 is not likely that any extraordinary fluctuations occurred during this 

 time. After 1 a. m., the observations were made hourly, and during a 

 considerable portion of the time they were half -hourly. It will be 

 seen, however, that a very important portion of the curve, from 10 

 p. M. to 1 A. M., is doubtful, and it is not at all unlikely that, had inter- 

 mediate observations been recorded, the fall of the barometer would 

 have appeared much more sudden than it does. The minimum ob- 

 served height was 28"735 inches at 2 a. m. At three o'clock the height 

 was only a trifle greater than this, and, from the nature of the curve 

 before and after the interval from two to three o'clock as well as from 

 the velocity of the wind, it seems highly probable that between these 

 hours a lower point than any observed was reached. The curve is con- 

 structed to show the actual vertical movement of the mercurial column. 

 From the minimum it rose rapidly until 6 a. m., at which hour the height 

 was 29'386 inches, and from that hour the rise continued with less 

 rapidity but with great steadiness, until the night of the following 

 Wednesday, when the reading was 30'378 inches. Thus the range of 

 the barometer in three days was 1*643 inches. This is more than two 

 tenths of an inch greater than the range for the whole of the last 

 year. At no time during last year did the barometer reach so low 

 a point as 29 inches, and the mean height for the year was 29"952 

 inches. 



The second chart shows the velocity of the wind at different hours, 

 extending over the same interval of time. These velocities are com- 

 puted from a continuous record made by an anemograph consisting 

 of a Robinson's anemometer with Beckley's registering apparatus at- 

 tached. From this curve it will be seen that, so far as the wind is 

 concerned, up to about 11 p. m., there were no indications of the coming 

 storm. At that time a breeze sprang up, which continued at less than 

 twenty miles per hour until about 1 A. m. when it suddenly increased 

 in velocity, and at 2 A. m. the record shows a speed of sixty miles 

 per hour. Unfortunately, shortly after two o'clock, the clock-work 

 which keeps the registering portion of the apparatus in motion was 

 stopped, the motion of the pendulum being undoubtedly arrested by a 

 sudden blast of great violence. This stoppage was not discovered until 

 3 A. M., so that between these hours the record is lost. At three o'clock 

 the instrument was put in motion again, and, for about fifteen or 

 twenty minutes after that hour, the record shows the extraordinary 

 velocity of ninety-five miles per hour. From this time the violence 

 diminished rapidly, a velocity of fifty miles per hour being registered 

 at 4 A. M., and at 5 a. m. it had fallen to less than twenty miles 

 per hour. Twice afterward, as will be seen by the chart, the speed 



