A. Because the electric fluid passes through air _extremely rarefied_: and whenever electric fluid passes through _air much rarefied_, it always produces a _white light_. Q. _Why are there sometimes DIFFERENT COLOURS in the aurora borealis, such as yellow, red, and purple?_ A. Because the electric fluid passes through _air of different densities_. The most _rarefied air_ produces a _white light_; the most _dry air, red_; and the most _damp_ produces _yellow_ streaks. Q. _Does the AURORA BOREALIS forbode fine weather or WET?_ A. When its _corruscations are very bright_, it is generally followed by stormy moist unsettled weather. Q. _Why does a HAZE round the SUN indicate RAIN?_ A. Because the _haze_ is caused by _very fine rain falling in the upper regions of the air_; when this is the case, a _rain_ of 5 _or_ 6 _hours continuance_, may be expected. Q. _Why is a HALO round the MOON a sure indication of RAIN?_ A. Because the halo is caused by _fine rain falling in the upper regions of the air_. The _larger_ the halo the _nearer the rain-clouds_, and the sooner may rain be expected. Q. _Why does a BLACK MIST bring WET weather?_ A. The mist is _black_, because it is _overshadowed by dense clouds_ or masses of vapour; and, therefore, it forebodes wet. Q. _Why does a WHITE MIST indicate FINE weather?_ A. The mist is _white_, because _no clouds blacken it with their shadow_; and (as the sky is cloudless) _fine weather_ may be expected. Q. _Why do we FEEL almost SUFFOCATED in a hot cloudy night?_ A. Because the heat of the earth (being unable to escape into the upper region of the air, in consequence of the clouds) _floats_, like a sea of heat, _on the surface of the earth_. Q. _Why do we feel more SPRIGHTLY in a clear bright night?_ A. Because the heat of the earth can readily escape into the upper regions of the air, and is not confined and _pent-in by thick clouds_. Q. _Why do we FEEL DEPRESSED in SPIRITS on a WET murky DAY?_ A. 1st--Because when the air is laden with vapour, _it has less oxygen_. 2ndly--The air being lighter than usual, _does not balance the air in our body_: and 3rdly--Moist air has a tendency to relax the nervous system. Q. _What is meant by the "air balancing the air" in our body?_ A. The human body is filled with air of the same density as that around: if, therefore, we ascend into _purer air_, or descend into _denser air_, the balance is destroyed, and _we feel oppressed and suffocated_. Q. _Why do we feel OPPRESSED and SUFFOCATED if the air around is not of the SAME DENSITY as that in our body?_ A. If the air around be more dense, it will _squeeze our body in_ by its weight: if it be _less_ dense, the air in our body will _blow us out_. Q. _Why do PERSONS who ASCEND in BALLOONS FEEL PAIN in their eyes, ears and chest?_