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Scientific Intelligence . 
with no inconsiderable interest, the following meteorological fact, 
the authenticity of which I am able to certify. From the 1st 
to the 24th of February, there fell upon the Isle of Cayenne 
twelve feet seven inches of water. This observation was made 
by a person of the highest veracity ; and I assured myself, by 
exposing a vessel in the middle of my yard, that there fell in 
the city ten and a quarter inches pf water between eight in the 
evening and six in the morning of the 14th and 15th of that 
month. From these enormous rains has resulted an inundation 
from which every plantation has suffered. 
11. Great Dryness of the Air at Perth. — The dryness of the 
air at Perth on the 18th of June, was greater, according to the 
hygrometric formula of Mr Anderson, than it has been observed 
on any former occasion, with suitable instruments. While a 
naked thermometer stood in the shade at 78°, one covered with 
moistened cambric was so low as 60°. The difference, amount- 
ing to 1 8°, indicated that the air was so partially charged with 
humidity, that it could have retained in the state of vapour 
more than double the quantity of water, which it actually held 
in solution. The evaporation, estimated by means of two in- 
struments of great delicacy lately invented by Mr Anderson, 
was at the rate of ~th of an inch per hour from 8 to 6 o’clock 
p. m. If the evaporation were to proceed at this extraordinary 
rate during the whole month, it wxmld amount, in thirty days, 
to about 14 inches of perpendicular depth. The low tempera- 
ture of the night, however, which (for reasons Mr Anderson 
explained in a paper read before the Literary and Antiquarian 
Society) always attends a dry state of the atmosphere, must re- 
duce it greatly below the calculations ; insomuch, that it would 
probably be rated too high even at a third part of what has been 
stated, actual evaporation for the past part of the present month 
being only S^th inches. 
HYDRODYNAMICS. 
12 . New Steam-Engine of great Power. — We understand 
that Mr Perkins has invented a new steam-engine, founded on a 
new property in steam, by which more than seven-eighths of the 
fuel hnd weight of engine may be saved. He has constructed 
a small one, with a cylinder two inches in diameter, and a stroke 
of twelve inches, which has the power of seven horses. 
