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1858.]
PROFESSOR NECREE'S LETTER.
179
in elucidation of it I made a little drawing, of which I
give you here a copy: it will, with the explanation and the
annexed diagram (Fig. 9), impart to you, I hope, a correct
idea of the phenomenon. You must conceive the observer
placed at the foot of a hill interposed between him and the
place where the sun is rising, and thus entirely in the
shade; the upper margin of the mountain is covered with
woods or detached trees and shrubs, which are projected
as dark objects on a very bright and clear sky, except at
the very place where the sun is just going to rise, for
there all the trees and shrubs bordering the margin are
entirely,—branches, leaves, stem and all,—of a pure and
brilliant white, appearing extremely bright and luminous,
although projected on a most brilliant and luminous sky,
as that part of it which surrounds the sun always is. All
the minutest details, leaves, twigs, &c, are most delicately
preserved, and you would fancy you saw these trees and
forests made of the purest silver, with all the skill of the
most expert workman. The swallows and other birds
flying in those particular spots appear like sparks of the
most brilliant white. Unfortunately, all these details,
which add so much to the beauty of this splendid phenomenon, cannot be represented in such small sketches.
" Neither the hour of the day nor the angle which the
object makes with the observer appears to have any effect;
for on some occasions I have seen the phenomenon take
place at a very early hour in the morning. Yesterday it
was 10 a.m., when I saw it as represented in Fig. 10. I
saw it again on the same day at 5 p.m., at a different
place of the same mountain, for which the sun was just
setting. At one time the angle of elevation of the lighted
white shrubs above the horizon of the spectator was about
20°, while at another place it was only 15°. But the
extent of the field of illumination is variable, according to
the distance at which the spectator is placed from it.
hi
.iid
If
m
P,
$$$
| Title | Tyndall, John, 1860, The Glaciers of the Alps. |
| Alternative Title | Glaciers of the Alps. |
| Creator | John Tyndall 1820-1893. |
| Subject |
Glaciers -- Alps. Alps -- Description and travel. Color. |
| Publisher | London : John Murray ... |
| DateOriginal | 1860 |
| Format | Tiff |
| Extent | 33 cm. |
| Identifier | col022 |
| Call Number | QE576.T914 1860 |
| Language | English |
| Relation | Color Science |
| Collection | Ice - 19th Century Polar Exploration & Glacial Studies |
| Rights | http://www.lindahall.org/imagerepro/ |
| Data Contributor | Linda Hall Library, LHL Digital Collections. |
| Title | Page 179. |
| Creator | John Tyndall 1820-1893. |
| Subject |
Glaciers -- Alps. Alps -- Description and travel. Color. |
| Publisher | London : John Murray ... |
| Format | tiff |
| Identifier | col022212 |
| Call Number | QE576.T914 1860 |
| Relation-Is part of | Is part of: The glaciers of the Alps : Being a narrative of excursions and ascents, an account of the origin and phenomena of glaciers, and an exposition of the physical princples to which they are related / By John Tyndall... |
| Relation | Color Science |
| Rights | http://www.lindahall.org/imagerepro/ |
| OCR Transcript | 1858.] PROFESSOR NECREE'S LETTER. 179 in elucidation of it I made a little drawing, of which I give you here a copy: it will, with the explanation and the annexed diagram (Fig. 9), impart to you, I hope, a correct idea of the phenomenon. You must conceive the observer placed at the foot of a hill interposed between him and the place where the sun is rising, and thus entirely in the shade; the upper margin of the mountain is covered with woods or detached trees and shrubs, which are projected as dark objects on a very bright and clear sky, except at the very place where the sun is just going to rise, for there all the trees and shrubs bordering the margin are entirely,—branches, leaves, stem and all,—of a pure and brilliant white, appearing extremely bright and luminous, although projected on a most brilliant and luminous sky, as that part of it which surrounds the sun always is. All the minutest details, leaves, twigs, &c, are most delicately preserved, and you would fancy you saw these trees and forests made of the purest silver, with all the skill of the most expert workman. The swallows and other birds flying in those particular spots appear like sparks of the most brilliant white. Unfortunately, all these details, which add so much to the beauty of this splendid phenomenon, cannot be represented in such small sketches. " Neither the hour of the day nor the angle which the object makes with the observer appears to have any effect; for on some occasions I have seen the phenomenon take place at a very early hour in the morning. Yesterday it was 10 a.m., when I saw it as represented in Fig. 10. I saw it again on the same day at 5 p.m., at a different place of the same mountain, for which the sun was just setting. At one time the angle of elevation of the lighted white shrubs above the horizon of the spectator was about 20°, while at another place it was only 15°. But the extent of the field of illumination is variable, according to the distance at which the spectator is placed from it. hi .iid If m P, $$$ |
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