EXTRACTS_NATURAL HISTORY. 
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tive capabilities, when seen at a distance, has a deep-blue appearance exactly si¬ 
milar to the atmosphere. It cannot be the medium of the air, through which it 
is seen, that renders it of this colour; for if part of the mountain be covered with 
snow, which has strong reflective powers, this snow is still seen of a pure white 
colour. It has been ascertained too, that the atmosphere, when seen from the 
top of a very high mountain, has a deep-blue tint, approaching to black, and 
this tint becomes deeper the higher you ascend. It may be observed also, that 
the centre of the atmosphere, looking perpendicularly upwards, always appear of 
a deep blue colour, which gradually passes to a white appearance towards the 
extreme verge of the horizon, or in the lower strata next the earth. Here most 
dense air is accumulated, and here the reflection is most perfect, or nearly ap¬ 
proaching to white light; whereas, perpendicularly overheard the rays of light 
pass through less of this air, the reflection is fainter, and hence the deeper blue 
colour.—W. Rhind.— Field. Nat. Mag ; 
Objections to the received Theory of Rain. —It is the received opin¬ 
ion, that rain is caused by the heat of the Sun’s rays raising the water in a state 
of vapour, into the higher regions of the atmosphere, and being there condensed 
by the cold, descends again, and thus forms rain. 
Objection First. —That water requires a heat equal to sixty degrees of Fah. 
thermometer, to raise it into vapour, according to the commonly received opin¬ 
ion, when experience proves that we have the most rain when it stands below 
temperate, which is 55 degrees; for instance, the snow in frost, and the rain after. 
Objection Second. —That when we have the greatest heat, with the largest loss 
of water, we have the least rain, as witness every diy summer. 
Objection Third. —When vapour is condensed into water, which it must 
be, if exposed to an atmosphere colder than itself, it must immediately de¬ 
scend, as witness the dews; it being the heavier in its specific gravity than the 
bulk of the surrounding atmosphere. Therefore, were water raised into vapour, 
by the heat of 300 degrees, it must be immediately condensed by the sudden 
change of temperature, and descend before it had risen to the height of one 
hundred yards, much less rise into the highest regions of the atmosphere, and 
remain there for a length of time, and then form clouds, and so produce rain, as 
witness the steam arising from the boiler of a steam -engine, or the refrigeratory 
of a common alembic. 
Objection Fourth. —Experience has proved that we have the most rain in 
nights, and in winter, when of course it must be the coldest, as then the Sun has 
the least influence. 
Objection Fifth. —There is no vapour arises from the water when the Sun has 
the most influence; for place a looking-glass over a river, when the Sun shines 
with his meridian force, and it will not so much as dim it; but when the Sun is 
gone down, the vapour rises so as to be visible. 
Objection Sixth. —If the old theoiy was true, there would always be the most 
rain in the tropics, where the Sun is vertical, which is not the fact.— Field’s 
Naturalists’ Magazine. 
