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test was no longer uncertain. Before the end of May, 1858, British rule was re-established throughout India.

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SCIENCE AND POETRY.

N one of his Irish melodies, so familiar to all lovers of poetry and music, Moore has the following lines:

"Oh! had we some bright little isle of our own,

In a blue summer ocean far off and alone,

Where a leaf never dies in the still blooming bowers,
And the bee banquets on through a whole year of flowers;
Where the sun loves to pause

With so fond a delay,

That the night only draws

A thin veil o'er the day;

Where simply to feel that we breathe, that we live,
Is worth the best joys that life elsewhere can give."

Now this is good poetry, but bad science. An "isle" in which "a leaf never dies," and in which the flowers bloom through the year, must necessarily be within the tropics-a latitude to which the succeeding lines about the "fond delay" of the sun, and the night which only draws a thin veil o'er the day," which, in other words, is a kind of twilight, are utterly inapplicable.1

The allusion and imagery which Moore loved to seek in certain parts of physical science were generally much more consistent with physical truth, without being less beautiful, than that which we quoted above. How happily, for example, did he avail himself of that beautiful property of the iris by which it accommodates the eye to greater and less degrees of light, enlarging the pupil when the light is faint, and contracting it when it is intense!

The iris, as is well known, is the coloured ring which

surrounds the dark spot in the middle of the eye; this dark spot being not a black substance, but a circular orifice through which the light is admitted to the membrane lining the posterior part of the internal chamber of the eye. The circular orifice is called the pupil, the retina being the nervous membrane which produces the visual perceptions.*

The iris which surrounds the pupil has a certain power of contraction and expansion, which is produced by the action upon it of proper muscles provided for that purpose. The quantity of light admitted through the pupil to the retina is increased or diminished in the proportion of the area of the pupil, which increases and diminishes in proportion to the square of its diameter; a very small variation of which, therefore, produces a very considerable proportionate variation of the quantity of light admitted.

If a person, after remaining for some time in a room dimly lighted, pass suddenly into one which is strongly illuminated, he will become instantly sensible of pain. in the retina, and will involuntarily close his eyes. After a short time, however, he will be enabled to open them and look around with impunity.

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The cause of this is easily explained. In the dimlylighted room the pupil was widely expanded, to collect the largest quantity possible of the faint light, so that a sufficient quantity might be received by the retina to produce a sensible perception of the surrounding objects. On passing into the strongly-illuminated room the expanded pupil admits so much of the intense light as to act painfully on the retina before there is time for the iris to adjust itself so as to contract the aperture of the pupil. After a short interval, however, this adjustment is made, and the area of the pupil being diminished

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in the same proportion as the intensity of the light to which it is exposed has been augmented in passing from one room to the other, the action upon the retina is proportionally mitigated, so that the eye can regard without pain the surrounding objects.

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The reverse of all this takes place when the eye suddenly passes from strong to feeble illumination. The pupil contracted when exposed to the strong light is not sufficiently open to admit the rays of feeble light necessary to produce visual perception, and for some time the surrounding objects are invisible. When, however, the proper muscular apparatus has had time to act upon the eye so as to enlarge the pupil, the rays are admitted in greater quantity, and the surrounding objects begin to be perceived.

These phenomena are beautifully expressed by the lines of Moore:

"Thus when the lamp that lighted

The traveller, at first goes out,

He feels awhile benighted,

And lingers on in fear and doubt.

But soon the prospect clearing,

In cloudless starlight on he treads,
And finds no lamp so cheering

As that light which heaven sheds."

Nevertheless, there is a point in this which demands some explanation. It is implied in these lines that the source of nocturnal illumination 11 on moonless nights is chiefly, if not exclusively, starlight. This has been in a great measure disproved by Arago, who shows that there must be some other source of nocturnal illumination than that of the stars. On nights, for example, which are thickly clouded, there is sometimes a stronger

light than on those in which the firmament is clear and serene. From this and other circumstances Arago argues that there must be some power of illumination in the clouds or in the atmosphere independently of the light which proceeds from the stars.

In another of Moore's poems we find the following beautiful lines :

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This is not only beautiful poetry, but sound astronomy. The distances of the stars are many hundreds of millions of times greater than that of the moon, but their actual splendour is in many cases greater than that of the sun. Thus it has been shown by calculations made upon observations which appear to admit of no doubt, that the star Sirius, commonly called the Dog Star, is a sun one hundred and forty-six and a half times more splendid than that which illuminates our system. Its distance, however, is so enormous that the actual light which it sheds upon our firmament is less than the five-thousand-millionth part of the sun's light. Abridged.

1 Utterly inapplicable. In tropical
regions the sun sinks very rapidly;
day changes into dark night with
scarcely any twilight between.

2 Posterior part, the back part.
3 Nervous membrane, coating full
of nerves.

4 Visual perception, act of perceiv
ing or noticing by the sight;
"visual" means relating to the
sight. (Lat. visus, sight.)

5 Which increases, that is, the area of the pupil increases.

6 Of which, of the diameter; that is, the distance across the middle.

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THE LOVE OF NATURE.

T is strange to observe the callousness1 of some men, before whom all the glories of heaven and earth pass in daily succession without touching their hearts, elevating their fancy, or leaving any durable remembrance. Even of those who pretend to sensibility, how many are there to whom the lustre of the rising or setting sun; the sparkling concave of the midnight sky; the mountain forest tossing and roaring to the storm, or warbling with all the melodies of a summer evening; the sweet interchange of hill and dale, shade and sunshine, grove, lawn, and water, which an extensive landscape offers to the view; the scenery of the ocean, so lovely, so majestic, and so tremendous; and the many pleasing varieties of the animal and vegetable kingdom -could never afford so much real satisfaction as the steams of a ball-room, or the wranglings of a cardtable.

But some minds there are of a different mould, who, even in the early part of life, receive from the contemplation of Nature a species of delight which they would hardly exchange for any other; and who, as avarice and ambition are not the infirmities of that

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