Page:Popular Science Monthly Volume 92.djvu/931

 Popular Science Monthly

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���The submerged dry dock was placed under the stern of the cruiser and then pumped out, thereby lifting the stem out o'f the water. This remarkable feat took place at Honolulu

��A Four-Hundred-Foot Ship in a Three-Hundred-Foot Dock

THE unusual feat of dry-docking a ship of four hundred and forty-six feet in length and a displacement of 9,300 tons in a dry dock only three hun- dred feet long and with a lifting capacity of 4,500 tons, was accomplished a short time ago, when the Japanese first-class cruiser Azuma, the propeller of which had been damaged, was docked for re- pairs in a floating dry dock at Honolulu. In order to carry out this undertaking, the dock was submerged and placed under the stern of the cruiser and then pumped out. It is said to have been the first time that this seemingly im.possible feat was attempted. The result was extremely gratifying, and the remarkable procedure is sure to find imitators elsewhere.

Thirty Million Collisions in a Day — the Earth's Record

ASTRONOMERS have collected a, great deal of material in recent years which seems to prove that there is an enormous mass of non-luminous comet or meteorite material scattered through stellar space. It is estimated that as

��many as twenty or thirty millions of such bodies collide with the earth every twenty-four hours. Assuming a fairly even distribution of these cosmic particles in space, their quantity and number must be beyond computation. Clouds of such particles are now believed to be the cause of the dark and starless areas in regions where bright stars are numerous. It is assumed that clouds of meteorite material prevent us from seeing the stars beyond in these particular regions of space. The dark spaces in the Milky Way, the so- called "coal sacks" in the constellation of Sagittarius and many other starless re- gions are accounted for in this manner.

Photographic star records made at Harvard and elsewhere during recent years have supplied much valuable in- formation to support the theory that the so-called new stars, also known as tem- porary stars, which flash out at points where previously no stars were known to exist, are stars which suddenly become luminous by passing through a cloud of meteoric particles. While passing through the cloud the faintly luminous star is in effect bombarded at high velocity by the meteoric cloud. The sur- face strata become heated and the lumi- nosity of the star increases rapidly.

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