10 
HINTS TO TRAVELLERS. 
should never fail to record cases of melting and solidifying of any sub¬ 
stances due to changes of temperature. The softening of candles and the 
freezing of mercury or of spirits give information regarding temperature 
at least as valuable as the readings of thermometers. 
Other Observations .—Any peculiar atmospheric phenomena, such as the 
appearance of the zodiacal light after sunset, the aurora, the electrical 
lights seen on pointed objects, and known as St. Elmo’s fire, rainbows, 
especially lunar rainbows, haloes, the appearance of mock-suns or moons, 
meteors or shooting stars, should be noted on their occurrence, as many 
of them are valuable weather prognostics. Attention should also be 
given to any appearances of mirage, or other effects of irregular distribu¬ 
tion of atmospheric density. Mirages are only rarely so perfect as to 
show, ships inverted in the air, palm-grown islands in the sea, or distant 
oases in the desert. The common form is an unusual intensification of 
refraction, raising land below the horizon into sight, or apparently 
cutting off the edges of headlands or islands at sea or on large lakes. It 
is worth while observing the temperature of the air and of the water or 
ground when an unusually clear mirage effect is visible. 
Another interesting series of observations may be made on the colours 
of the sky and clouds at sunrise and sunset. A phenomenon often 
observed at sunset, but the existence of which is still sometimes denied, 
should be looked for. This is the appearance of a flash of coloured light 
at the moment when the upper edge of the sun dips below a cloudless 
horizon. A note should be made of the nature of the horizon, whether 
land or sea, and of the colour of the light if it should be observed. When 
opportunity offers, the first ray of the rising sun might be similarly 
observed. 
The traveller should, at the end of each day, give his opinion of the 
nature of the weather, saying whether he felt it hot or cold, relaxing or 
bracing, close or fresh. Such observations have no necessary relation to 
degree of temperature or humidity as recorded by instruments; but the 
human body is the most important of all instruments, and everything 
which affects it should be studied. By paying attention to the foregoing 
instructions, an observant traveller will bring home a far better meteoro¬ 
logical log without instruments than a more careless person could 
produce by the diligent reading of many scales. Yet, in enforcing the 
importance of non-instrumental [observations, we must not leave the 
