Page:Popular Mechanics 1928 11.pdf/52

 

When flyers skim too low over the city of San Diego, Calif., perform dangerous stunts against the air regulations, or otherwise jeopardize traffic, a police plane takes off, flies alongside the offender and informs the pilot by the message written on the side of the ship to stop his acrobatics and "Land at Once." The force has been organized by the San Diego board of air control and is expected to prove a valuable aid to aviation at this port, where traffic of the skies is almost daily becoming more congested. The written order was decided upon to make identification of the police plane easy and to save the patrolmen's voices as it would be almost impossible to yell the orders loud enough to make them heard above the roar of the motors.

 

That some of the Roman blades which conquered the world of their time was of a workmanship that later became known by the name of Damascus, is the interesting conclusion of Prof. B. Neumann, of the Institute of Technology at Breslau. He has just completed an extensive research in metallurgy based on fragments of a number of Roman swords which were found buried in a German peat bed where they had lain for more than 1,600 years. Since they were preserved from the action of the air by the damp earth, they were in far better condition than other specimens of Roman steel. Apparently, the bars from which these swords were made, were prepared by sandwiching alternate thin layers of high and low-carbon steel and then "sweating" the whole together. Left straight, the bar could he forged into a blade with a striped or ribboned effect. Twisted and then forged, it produced a blade with a vee-damascening. Two twisted bars sweated together and then forged into a blade gave a W-pattern on the finished sword. Some of the Roman blades also show a curled or "rose" pattern, but how the smiths achieved this is not yet known. Professor Neumann's examination of the steel samples shows that the Romans tempered only the outside of the blade so that it would give a hard edge and point backed up by a tough body.

 

Motorcycles have been enlisted in the warfare against mosquitoes in suburbs of Chicago. A thirty-five-gallon tank of an acid tar oil is carried on the machine and the liquid is sprayed over small pools of water where the insects breed. The rider operates the spray hose without leaving his seat and, in a single day, can cover a wide territory. A district comprising more than seventy-five square miles, has been visited by the cycle throughout the season, and a marked reduction in the number of mosquitoes has been noticed.

¶ Sound passes through helium almost twice as fast as it does through air.

