STORMS ON THE COAST OF NEW SOUTH WALES. 81 
wee the clouds. Other flashes were observed, not perpendi- 
r, 10 seconds, 12 seconds, and so The stor wr iprege ust 
iesioxe have had an altitude of at eer 9,000 fee 
Now, taking the interval between the time at whi oe the first 
streak of sky was seen in the west, and the time at which the 
end of the storm cloud passed over ‘Byailey with an altitude of 
9,000 feet, as shown, ound the storm was moving at 
least 50 miles per hour gna taking the time of its passing 
Grenfell bo ey dis) velocity is found to be 68 sail per 
hour. w these storm clouds must have been more than 
200 00 miles i in diameter, for when the storm was breaking over 
Grenfell at 5 p.m, 170 miles west, they obscured the sky at 
Sydney. But the most remarkable fact about this storm is its 
effect ete ae barometer. At 6 o’clock, when aed eae eta 
be heard coming, the barometer sudde enly began rise, 
20 minutes bad risen 0°12 inch; and it is Socisiniia that i in ite 
middle of this rise it fell rapidly for 3 minutes and then began to 
rise again. (See copy of barograph sheet attached.) At 9°20, 
when the storm passed, an equally sudden fall set in for 20 
s, and again a check came in the middle, and the baro- 
rate of translation of the storm equal to 250 miles. Now, large 
as this will appear, I believe we have here a species of eyclone 
moving rapid] eshte the upper grag aiy with such force 
(68 miles per hour) that it increases the pressure in front of it, 
and causes a partial vacuum in its rear. fin y calculation 
t such:a mass of clouds ee through the air at the 
maintain its form. There ¢ , 1 think, be no pe about the 
velocity of its fianaiation: ca the explanation I have — 
the increase of pressure in front and the loss of it in 
seems the most probable. It may be remarked that sucha yan 
passing over us should disturb the surface air, and such was not 
