364 Meteorological Table. [May, 
The red oxide of mercury absorbing hydro-cyanic vapour with so 
much facility, I point it out as very proper to separate it from most 
of the gases with which it may be mixed. I have used it several 
times with success. 
From these few experiments, we see that the oxides produce 
different effects on hydro-cyanic vapour. Those in which the oxygen 
is strongly condensed disengage the hydrogen, and form cyanurets 
of the oxide; but the oxides in which the oxygen is weakly con- 
densed act upon it in so many ways that they require to be more 
accurately examined than I have done to obtain any general results. 
(Ze be continued. ) 
ARTICLE V. 
Meteorological Table: extracted from the Register kept at Rose- 
Bank, Perth. Latitude, 56° 25’. Elevation, 130 feet. Bya 
Young Gentleman of the Perth Academy. 
THE last column of theannexed table (Pl. XLVIIL.) contains, under 
the head Thermometer, the mean temperature of water from a well 25 
feet deep, taken three times every month, viz. onthe 5th, 15th, and 
25th. The extreme temperatures observed were 42°4° on the 5th 
and 15th of March, and 48°S° on the 25th of October and the 
5th of November, being an annual variation of 6°4°. This varia- 
tion may be easily accounted for en the commonly received theory 
of the origin of springs, of which it affords in its turn a beautiful 
illustration. The temperature of the atmosphere reaches its 
maximum about the end of July, and its minimum about the end 
of January. But as the influence of the sun’s rays in the one case, 
and the intensity of the frost in the other, cannot be supposed to 
penetrate to such a depth as directly to affect the temperature of 
water 25 feet below the surface, the change in that temperature as 
indicated in the table must have taken place at or near the surface 
of the ground. ‘This leads naturally and directly to the true theory 
of springs and wells, viz. that the water which is deposited on the 
higher grounds from the atmosphere descends through the earth as 
in a filter, till, being arrested by an impermeable stratum, it flews 
along the surface of that stratum, and either bursts out in springs, 
or is intercepted by pits dug for the purpose ; and this theory being 
admitted, it is easy te deduce from it the law of variation in the 
temperature of pump water. ‘The rain and melted snow of winter, 
being cooled down on their first entering the ground, far below the 
meai temperature of the interior of the globe, successively abstract 
from the strata through which they pass a portion of caloric; and 
though, from the quantity of water bearing so small a proportion to 
the body of earth through which it passes, that body cannot be re- 
