Light flash

“ Fixed and Flashing.—Fixed light varied by a single white or coloured flash, which may be preceded and followed by a short eclipse. This type of light, in consequence of the unequal intensities of the beams, is unreliable, and examples are now seldom installed although many are still in service. ”

“ A disposition of the mirrors, which, together with the greater quickness of the revolutions, which shows a flash once in five seconds of time, produces a very striking effect, totally different from that of a revolving light, and presenting the appearance of the flash alternately rising and sinking, the brightest and darkest periods being but momentary ”

“ As the light was turned successively upon one and another of the clusters of glass, sometimes it would flash along the whole line so rapidly that all the various combinations of color and motion seemed to be combined in one, and then for a time each particular set of fireworks would blaze, sparkle, and coruscate by itself, scattering particles of colored light as if they had been real sparks of fire. ”

“ The zigzag track of light across the darkened sky, with its accompanying crash, is one of nature’s exhibitions of tremendous power. The irregularity of its path is due to the resistance of the air, compressed by the electric motion. The beautiful illumination called heat or sheet lightning, is caused by the reflection of the electric flash, at a great distance from the observer. ”

“ Antonyms: LIGHT. Synonyms:
Light, strictly denoting a form of radiant energy, is used as a general term for any luminous effect discernible by the eye, from the faintest phosphorescence to the blaze of the noonday sun. A flame is both hot and luminous; if it contains few solid particles it will yield little light, tho it may afford intense heat, as in the case of a hydrogen-flame. A blaze is an extensive, brilliant flame. A flare is a wavering flame or blaze; a flash is a light that appears and disappears in an instant ”

“ Things which are smooth have the natural property of shining in darkness, without, however, producing light. Now, the part of the eye called 'the black', i.e. its central part, is manifestly smooth. The phenomenon of the flash occurs only when the eye is moved, because only then could it possibly occur that the same one object should become as it were two. The rapidity of the movement has the effect of making that which sees and that which is seen seem different from one another. Hence the phenomenon does not occur unless the motion is rapid and takes place in darkness. ”

“ While the lightning flash shows the brilliancy which the electric illumination can attain, it shows also the intense heat resulting from the electric discharge. This might, indeed, be inferred simply from the brilliancy of the light, since we know that this brilliancy can only be due to the intense heat to which the particles along the track of the electric flash have been raised. But it is shown in a more convincing manner to ordinary apprehension by the effects which the lightning flash produces where—in the common way of speaking—it strikes. The least fusible substances are melted. ”

“ The splendid appearance of colored polar light is the act of discharge, the termination of a magnetic storm, as in an electrical storm a development of light — the flash of lightning — indicates the restoration of the disturbed equilibrium in the distribution of the electricity. ”

“ If we stand on an eminence commanding a view of a number of cannon, say a mile distant, which the soldiery are from time to time firing, a decided difference of time will be perceived between the flash and the report; the same observation applies to lightning, a considerable interval often occurring between the flash and the thunder. Hence, light is said to travel faster than sound. ”

“ The glare of the sun that is reflected from each point of the surface of a mirror forms a cone of light whose vertical angle is constant, and equal to that subtended by the sun. Hence when a flash is sent to a distant place, the size of the mirror is of no appreciable importance in affecting the size of the area over which the flash is visible. ”

“ The clouds will sometimes assume the most fantastic forms, and at other times will be irradiated with beams of light, or, covered with the darkest hues, will assume a lowering aspect, prognostive of the thunder’s roar and the lightning’s flash—all in accordance with the different rays that are reflected to our eyes, or the quantity absorbed by the vapours which float in the atmosphere. ”

“ Every time that the flashing light gains or loses one complete flash, upon the motion of the tuning-fork, it will appear to make one complete oscillation, and the water-drops will appear to move back or on one place. ”

“ An alternating light is one in which two colors are shown each for an equal interval with no intervening eclipse, but if an eclipse separates the color flash from a white flash, for instance, it becomes a flashing white light varied by a red flash. It is a very common practice to insert sectors of [Pg 154] different colors into the arc of visibility of a light in order to cover a dangerous shoal or to indicate a channel. ”

“ Hence, if a man watches the play of the flash from his mirror upon a very near object, it will appear to him of the shape and size of the mirror; but as he retreats from the object, the edges of the flash become rounded, and very soon the flash appears a perfect circle, of precisely the same apparent diameter as the disc of the sun: it will, in short, look just like a very faint sun. The signaller has to cause this disc of light to cover the person whose notice he wishes to attract. ”

“ The ones at the left either rest upon or are hidden behind a rise of ground, whose crest can be traced for a little distance each side of the flash, while those at the right come lower, falling between the observer and the ground at that point. Probably, when measured upon this diagonal and curved line, the width of the flash was fifteen or twenty feet.
Mention has already been made of the fact that the accompanying thunder was comparatively light, and not at all like that ordinarily heard when lightning occurs within so short a distance. ”

“ But not only must we seek the measure of motions and actions by themselves, but much more in comparison; for this is of excellent use and very general application. Now we find that the flash of a gun is seen sooner than its report is heard; [p. 212] although the ball must necessarily strike the air before the flame behind it can get out; and this is owing it seems to the motion of light being more rapid than that of sound. We find too that visible images are received by the sight faster than they are dismissed; ”

“ "I was thinking of very old times, when the Romans first came here, nineteen hundred years ago—the other day. . . . Light came out of this river since—you say Knights? Yes; but it is like a running blaze on a plain, like a flash of lightning in the clouds. We live in the flicker—may it last as long as the old earth keeps rolling! But darkness was here yesterday. ”

“ A BOHEMIAN observer, M. Robert Haensel, of Reichenberg, has succeeded in accurately photographing a flash of lightning. His pictures, of which he has taken several, show the light of the flash, under the form of long, continuous sparks, traversing the atmosphere. With the spark the landscape also is well produced, and a means is ”

“ But if we suppose that a flash of lightning, in a particular case, lasts for the thousandth of a second, it would follow, from the above experiments, that the flash is a hundred times as bright, in fact, as it appears to the eye. ”

“ It had just so happened that I had become interested in what are side flashes, or what are called "supplementary" ones. Now the question has been mooted as to what is the character of what seems to our vision to be second flashes—that is, apparent flights of electrical fluid coincident with the first or strongest one, and some scientific men think that as often as not we see the reflection of the important flash mirrored by the clouds in many different directions. ”

“ It is certain, then, that the eye's estimate of the intensity of the illumination resulting from a lightning flash is far short of the truth. This is equally true even in those cases where lightning is said to be for awhile continuous. If the flashes for a time succeed each other at less intervals than a twenty-fifth of a second, the illumination will appear continuous. ”

“ Diffused lightning is the commonest of all. You can count hundreds of flashes on a stormy night. Occasionally they succeed one another with such rapidity that the sky is momentarily entirely illumined with a fantastic brightness. At these times great sombre clouds can be seen surging from the darkness of the night, to shine suddenly with an ephemeral brightness of a diffused red, blue, or violet tinge. Their irregular shapes, with their jagged edges of light, are visible against the dark background of the heavens, and the thunder growls monotonously. ”

“ If two persons are standing in a room looking different ways, and a loud clap of thunder, accompanied with zigzag lightning, happens, they will both distinctly see the flash, not only by that indistinct illumination of the atmosphere which is occasioned by fire of any kind, but the very form of the lightning itself, and every angle it makes in its course, will be as distinctly perceptible as if both had looked directly at the cloud from whence it proceeded. ”

“ The lightning, which till now had shaken quivering lances of flame across the black water, a flash, then darkness, then again a flash, now became continuous, playing in lambent flames amid the blackness, lighting up the wild turmoil of wind and wave and cloud. ”

“ The flash is seen, the thunder heard, and the clouds open their watery store-house, a few distant and heavy drops increasing into a cataract of rain. Flash rapidly follows flash, and the interval between each appearance and the accompanying thunder peal becomes less. The pale hue of the lightning is exchanged for a vivid glare, in which a deep yellow, red, or blue is the predominant color, a variety of aberrations marking its course, the zigzag form showing that the fearful agent is near terrestrial objects. ”

“ A body illuminated by an instantaneous flash continues to be seen for the sixth of a second after the flash has become extinct; and if the body thus illuminated be in motion, it appears at rest at the place where the flash falls upon it. When a colour-top with differently-coloured sectors is caused to spin rapidly the colours blend together. Such a top, rotating in a dark room and illuminated by an electric spark, appears motionless, each distinct colour being clearly seen. ”

“ It is supposed by many, that when the spark is long enough we can note the direction in which it travels; and observations of the motion of lightning from the earth to the cloud have been collected, as showing that the usually observed direction of the flash is sometimes reversed. In reality, no one has ever seen a lightning flash travel either one way or the other. If the attention is fixed on the storm cloud, as usual when a lightning storm is watched, every flash appears to pass from the cloud to the earth. ”

“ In certain conditions of the atmosphere it is possible for the fixed light of low power to be entirely obscured while the flashes are visible, thus vitiating the true characteristic of the light. Cases have frequently occurred of such lights being mistaken for, and even described in lists of light as, revolving or flashing lights. ”

“ In the lighter storms thirty and thirty-five flashes may be counted in a minute: so vivid is the glare that it discloses the finest shades of colour, and appears followed by a thick and palpable gloom, such as would hang before a blind man’s eyes, whilst a deafening roar simultaneously following the flash, seems to travel, as it were, to and fro overhead. ”

“ Sometimes glowing spots appeared in the dark band, again streamers of light shot up to the zenith, the center of brightness constantly shifting, as the flames died out in one place to flare up in another. ”

“ When the dark intervals occur, the rays from the flame which are then pointing toward the obscure spaces, have their direction so altered laterally as to pass into the adjoining bright places; and so increase the power of the luminous flashes. A revolving light, though supplied by a flame of the same strength as a fixed, will thus necessarily be raised to a higher degree; for it does not lose its power by diffusing the rays constantly over the whole horizon, but gathers them up into a number of separate beams of greater intensity. ”

“ First, if we accept the results arrived at by Professor Ogden Rood, of Columbia College, what appears to the eye as a single flash of lightning, consists, in fact, as a general rule, of a succession of flashes, each one of which must naturally produce its own peal of thunder; and although the several flashes, if they follow one another at intervals of the tenth of a second, will make one continuous impression on the eye, the several peals of thunder, under the same conditions, will impress the ear as so many distinct peals. ”

“ Section I.—The purpose which a Lightning Conductor is intended to serve. A flash of lightning is the passage of an electric spark between two bodies oppositely or unequally electrified, and between which the difference of electric pressure or potential is sufficiently strong to break across the air space which separates them, and to produce what is known as a disruptive discharge. A flash may pass either between one cloud and another, or between a cloud and the earth. ”

“ This keeper remarked that the centre of the flame should be exactly opposite the centre of the reflectors, and that accordingly, if he was not careful to turn down his wicks in the morning, the sun falling on the reflectors on the south side of the building would set fire to them, like a burning-glass, in the coldest day, and he would look up at noon and see them all lighted! When your light is ready to give light, it is readiest to receive it, and the sun will light it. ”