METEOROLOGY AND CLIMATOLOGY. 
23 
shows the highest temperature since it was last set. Before reading 
the thermometer, it is well to take the precaution of seeing that the 
inner end of the thread of mercury is in contact with the constriction 
in the tube, and if by the shaking of the instrument or otherwise, the 
mercury has slipped away from this position, if should be brought back 
to it by tilting the thermometer bulb downwards very gently, then 
returning it to the horizontal position and reading. 
To set this thermometer, it is only necessary to hold it vertically bulb 
downwards and shake it, if necessary striking the lower end of the frame 
carrying the instrument, gently against the palm of the hand. This 
causes the mercury to pass the constriction and re-enter the bulb. When 
set, the end of the column farther from the bulb should indicate the 
same temperature as the ordinary dry-bulb thermometer. 
Another form of maximum thermometer is known as Phillips 5 . It is 
an ordinary mercurial thermometer, but a short length of the upper part 
of the column in the tube is separated from the rest by a little bubble of 
air. It is used in the horizontal position, and as the temperature rises 
the whole column moves forward, while, when the temperature falls, only 
that portion behind the air-bubble retires towards the bulb. The tip of 
the column thus remains to mark the maximum temperature to which its 
farther end points. The instrument is set by gently tilting the bulb end 
downward, when the detached portion of the column at once runs back 
until stopped by the air-bubble. This is the most convenient instrument 
to use at a fixed station; but in travelling it is apt to get out of order, 
as shaking may have the effect of allowing the air-bubble to escape into 
the upper part of the tube, or into the bulb, and the instrument cannot 
easily be brought into working order again. 
Bain- Gauge .—While measurements of rainfall can possess no climato¬ 
logical value unless they are carried on continuously at a fixed station 
some very interesting observations may be made by the traveller both 
during the night when in camp, and during heavy showers when compelled 
to stop on the march. The rain-gauge is in itself the most simple of all 
scientific instruments, for it consists merely of a copper funnel to collect 
the rain as it falls, and a bottle to contain what has been collected. A 
graduated measuring glass is the only accessory required. Rain is measured 
by the depth to which the water would lie on level ground if none 
soaked in, evaporated or flowed away. On an emergency, a rain-gauge 
