24 
receiving surface of which is accurately turned in a lathe, and termi- 
nated at its lower extremity by a bent tube of small aperture, in 
which the last few drops of rain remain.” The funnel is fitted accurately 
on to the cylindrical ee vessel, in such a manner that no water 
can escape by evaporation. The object of retaining the last few drops 
of rain in the tube of the funnel, is that they prevent any vapour 
from passing off from the water contained in the receiving vessel. The 
glass measure is graduated to hundredths of inches. As it is very much 
narrower than the receiving surface, half-an-inch of rain is represented 
by about seven inches in the measure. It has been calculated that one 
inch of rain falling in the quadrangle is equivalent to about 61780 gallons. 
“The maximum thermometer consists of a bulb and tube of mercury 
fitted on a porcelain scale, with the divisions engraved on the glass tube. 
The thermometer tube above the mercury is entirely free from air ; and 
in a bend above the bulb, is inserted and fixed with the blow-pipe, a 
small piece of solid glass, or enamel, which acts as a valve, allowing mercury 
to pass on one side of it when heat is applied ; but ot allowing it to return 
when the thermometer cools. When mercury has been once made to pass 
the valve, which nothing but heat can effect, and has risen in the tube, 
the upper end of the column registers the maximum temperature. To 
return the mercury to the bulb, we must apply a force equal to that 
which raised it in the tube ; the force employed is gravity, and is applied 
by simply lowering the bulb end of the thermometer, when the gravity 
of the mercury in the tube will be sufficient to unite it with that in the 
bulb, and thus prepare the instrument for future observation.” 
“The minimum thermometer consists of a glass tube, the bulb and 
part of the bore of which is filled with pure alcohol, in which floats freely 
a black glass index. A slight elevation of the thermometer, bulb ae 
most, will cause the glass index to flow to the surface of the liquid, where 
it will remain unless violently shaken. If the temperature falls, the 
alcohol contracts and takes the index with it ; if the temperature rises 
it leaves the index behind, which thus shows the lowest temperature at 
which the thermometer has been since it was last set.” On December 3rd, 
this instrument was found broken ; it is unknown how or by whom. 
new thermometer has been procured at the expense of the Society. 
The wet and dry bulb thermometer, which could not be put up before 
for want of a sheltered position, has just had a roof constructed forit. It 
consists of two thermometers, one of which is an ordinary thermometer, 
and the other has its bulb covered with muslin, which is kept wet by con- 
nection with a vessel of water. The object of this instrument is to show 
the amount of moisture contained in the air. The principle of its action 
is that the dryer the air is, the faster the water on the muslin evaporates, 
and in doing abstracts the more heat from‘the wet bulb. Thus the differ- 
ence betwen the indications of the wet and the dry bulb thermometers 
(of course, the wet bulb is lowest) indicates the dryness of the air. If the 
air is saturated with moisture they coincide ; in very dry climates there is 
sometimes as much as 30° Fahrenheit difference between them. : 
The largest falls of rain which have been measured here are 1.50 in. 
cape 24th), 1.39 in. (July 12th), 1.07 in. (September 30). 
he highest and lowest temperatures have been respectively 83° 
Fahrenheit (July 21st and 23rd), and 26° (December 10th). I 
