After suggesting that the refraction of the rays in the
atmosphere may be due to what he calls its 'lenticular outline,' he
defines refraction to be 'the bending of a ray passing obliquely from a
rarer into a denser medium,'--a good enough popular definition, but for
its sad defectiveness. Is he not aware that the light is also bent in
penetrating obliquely from a denser into a rarer medium, as in passing
from the surface of a low plain to the eye of a spectator on a
neighboring mountain, and that the bending is just as great in this
direction of its motion as in the other? And does he not know that it
changes its course whenever it passes from a vacuum into any ponderable
medium or in the opposite direction? In future attempts to make
science easy, let him remember that these are all equally instances of
refraction, and should be included in its definition.
"Under the same head, we are led to infer that it is only in 'the warm
and moist nights of summer,' that 'the moon, as she rises above the
horizon, appears much larger than when at the zenith'; and we are
taught, in connection with the origin of the mirage and the spectre
of the Bracken, that 'rainbows are due to this condition of the
atmosphere.' If, instead of rainbows, we may be allowed to read _halos_,
we can understand the writer, who, instead of thinking of summer
showers, appears to have had a _haze_ in his mind while penning this and
other paragraphs.
Pages:
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326