Page:Littell's Living Age - Volume 134.djvu/518

512 "When one of the seekers has discovered one, he will frequently hide it until its mate is found. "Mr. Streeter knows of only one specimen of a red diamond, which is like a gem on fire, and it passed from his hands into the possession of a great connoisseur last year. "The red diamond," wrote Sir Thomas Nicols, in 1651, "is prized according to the glorious beauty of its perfection. It feeds your eyes with much pleasure of beholding, and hence are discovered to us the excellency of super-celestial things."

There is something fascinating to the imagination in the experiments which have been tried on diamonds in order to wrest the secret of their nature and their formation from them. One cannot read without a feeling of suspense how the Accademia del Cimento, in the year 1694, induced by Cosmo III., fixed a diamond in the focus of a great burning-glass, and watched it, dismayed, as it cracked, confiscated, and disappeared; and how the experiment was frequently repeated, until Lavoisier (he whom Fouquier Tinville declared to be unnecessary to the republic) proved that diamonds burn just the same as common coal, if oxygen be not shut out, because they are pure carbon and combine with oxygen. How silent and how still one would have stood to watch Guyton de Morveau at his work, when he consumed a diamond in oxygen by means of the burning-glass: "First, he saw on that corner of the diamond which was in the exact focus of the lens a black point; then the diamond became black and carbonized. A moment after, he saw clearly a bright spark, twinkling on the dark ground; and when the light was interrupted, the diamond was red-hot and transparent. A cloud, and the diamond was more beautifully white than at first; but as the sun again shone forth in its full strength, the surface assumed a metallic lustre. Up to this point, the diamond had sensibly decreased in bulk, not being more than a fourth of its original size; of elongated form, without definite angles; intensely white, and beautifully transparent. The experiment was suspended for a day or two, when, on its resumption, the same phenomena recurred, but in a more marked degree; subsequently, the diamond entirely disappeared," — like Macbeth's witches, making itself — air!

 

  — It is well known that if a mirror be attached to a vibrating tuning-fork, and a point of light which moves uniformly in a plane at right angles to that in which the fork is vibrating be reflected from this mirror, the image will be an ordinary single wave. Again, if a series of luminous points move uniformly with such velocity that a point passes over two intervals during an odd number of vibrations of the fork, the two waves overlap and produce a double figure of the form of a series of figures-of-eight. Extending these principles, Professor McLeod and Lieutenant G. S. Clarke have recently constructed an ingenious apparatus which has been described before the Royal Society under the name of the cycloscope. Equidistant perforations are made in a circle on a disc, which is attached to a rotating axis, and the light passing through these apertures falls upon a vibrating tuning-fork of known period, whence it is reflected on to a screen; and from the shape of this reflected image the rate of rotation can be deduced. Hence the cycloscope promises to become of much value in determining the speed of machinery. On the contrary, if the speed at which the cylinder rotates be known, the pitch of the tuning-fork may be ascertained.

— The greatest feat of an Arab hunter is to capture an ostrich. Being very shy and cautious, and living on the sandy plains, where there is little chance to take it by surprise, it can be captured only by a well-planned and long-continued pursuit on the swiftest horse. The ostrich has two curious habits in running when alarmed. It always starts with outspread wings against the wind, so that it can scent the approach of an enemy. Its sense of smell is so keen that it can detect a person a great distance long before he can be seen. The other curious habit is that of running in a circle. Usually five or six ostriches are found in company. When discovered, part of the hunters, mounted on fleet horses, will pursue the birds; while the other hunters will gallop away at right angles to the course the ostriches have taken. When these hunters think they have gone far enough to cross the path the birds will be likely to take, they watch upon some rise of ground for their approach. If the hunters hit the right place and see the ostriches, they at once start in pursuit with fresh horses, and sometimes they overtake one or two of the birds; but often one or two of the fleet horses fall, completely tired out with so sharp a chase. 