THE DEVELOPMENT OF METEOROLOGY. 
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base was 12,400 feet, and its total height above the ocean 
level was 16,000 feet. The spray, or cascade of drops form- 
ing a cloudy or smoky appearance at the base of the spout, 
was 720 feet in diameter, and the height of the summit of 
this cascade was 420 feet. 
As a small vessel is visible in the middle of some of these 
pictures, I will add that the distance from the photographic 
camera at Cottage City to the waterspout was 5.75 miles, but 
the distance to the schooner was only 2 miles ; the movement 
of the waterspout from the northwest to the southeast was at 
the rate of about 1.10 miles per hour; the rate of the schooner 
was 1.7 miles per hour. The wind was very light at the 
time, as stated by several observers and as shown by the 
smoothness of the water. Meteorological observations are 
rather scanty, but from the best information at hand Pro- 
fessor Bigelow finds the average temperature of the air at sea- 
level at the place of the spout was 67.5° F., or the maximum 
for the day, and the thermograph for Nantucket also shows 
that the spout occurred at the time of maximum temperature. 
On the other hand, the temperature at the land stations fell 
rather rapidly to 56.5° at Vineyard Haven and 59.0° at 
Woods Hole; so that the effective temperature within the 
anti-cyclonic wind that prevailed around the outside of the 
cloud, or at a distance from the spout, was about 58°. The 
barometric pressure in this outside region was about 30.10 
inches, but must have been about 30.05 near the waterspout. 
The relative humidity was low at the meteorological station. 
The lower strata of the atmosphere were drier than on any 
other day of the month, and after several trial computations 
Professor Bigelow accepts a relative humidity of 64 per cent 
as prevailing in general near the surface of the water at the 
time the waterspout was formed. These are the meteor- 
ological data at sea-level beneath the cloud which surmounted 
the waterspout. This cloud was a large cumulo-nimbus, 
with its flat base about 3,600 feet above sea-level, as just 
stated in connection with the length of the tube. With these 
meteorological data and the thermodynamic equations, Pro- 
fessor Bigelow computes the conditions in the air ascending 
in a rapid whirl within the center of the tube. 
