Page:Popular Science Monthly Volume 90.djvu/924

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��Popular Science Monthly

��In 1 90 1, for example, there appeared the brilHant new star Nova Persei. Long exposure photographs showed that the star was enveloped by an extensive and beautiful nebula. That was in itself not remarkable. But a second exposure made several weeks later showed that the shape of the nebula had changed and that it had ex- panded out- ward. Astrono- mers were be- wildered. The star is so very distant from us that it takes its light centuries to reach us. We saw it on the plates, not as it appeared when the exposures were made, but as it appeared long before the steam engine was invented, long before there were rail- roads. Obvious- ly, the real dis- tance in miles traveled by this expanding por- tion of the neb- ula must have been enormous. Attempt after attempt was made to explain this apparently

incredible phenomenon ; but nothing really satisfactory has yet been suggested.

Far less dramatic, but of immense value, is the photographic work done at Harvard in mapping the sky. The map is not made once for all, but its separate sections are constantly rephotographed. The plates are stored in a fireproof building erected especially for the purpose. With such a photographic record, it becomes possible to study the past history of a star at any time. The study of these photographs constitutes a very important part of the work, which is done mostly by women.

��Freighting a Steamer by Means of a Marine Elevator

��A

���The platform of the elevator is brought to the level of the dock where it is quickly loaded. An electric motor then hoists it to the deck of the steamer

��vessel to be loaded at any time or tide, which doubles the normal rate of the load- ing and which re- duces expenses a corresponding amount is now being intro- duced all along our coasts. For- merly a coast steamer had tx> wait for the tide to come in be- fore she could steam up to the loading dock. Then the cargo was either hauled up by the ship's der- ricks piece by piece, or it was run up the gang- way by the truck load. But with the eleva- tor designed by Harry Barlow, ofSeattle, Wash- ington, an entire platform of ma- terial can be quickly carried up to the ves- sel's deck at once. And if the tide is out, the light sound boat carrying the elevator steams from the dock to the vessel anchored near by.

A small electric motor mounted on the top of the elevator structure furnishes the power for the half dozen cables used. The motor controls are placed at any point that affords the operator an unobstructed view. After the operator has brought the plat- form to the level of the loading dock, the filled platform can be easily raised up to the deck of the largest steamer. Level trucking is thus afforded in place of truck- ing up or down steeply inclined gangways. This fact makes the elevator indispensable for loading explosives or fragile wares.

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