Popular Science Monthly 



A Scientifically Designed Train- 

 Announcing Megaphone 



A GIGANTIC megaphone for an- 

 nouncing the arrival and departure 

 of trains at the Pennsylvania Railroad's 

 terminal in Washington, D. C., has been 

 developed to such a degree of success 

 that sounds emitted by it reach clearly 

 to every corner of the huge station, 

 despite the fact that the announcer is 

 not required to raise his voice much 

 higher than an ordinary conversational 

 tone. The megaphone, which is mount- 

 ed on a high wooden platform, is 

 interesting, not only because of its 

 gigantic proportions — for two men could 

 crawl inside and hide comfortably — but 

 also because it is the culmination, of a 

 great many painstaking experiments. 



A. M. Keppel, who is the designer, has 

 tried out in the huge horn almost every 

 applied principle of acoustics. A dozen 

 horns of various sizes, shapes and 

 groupings have been installed, improved 

 and discarded. The present megaphone 

 is considered to be the most satisfactory 

 of all. Probably the most important 

 discovery in connection with all of the 

 devices tried was that a flat horn 

 carries sound with fuller volume and 

 less distortion than a round horn of the 

 same general proportions. Accordingly, 

 a huge flat megaphone was built and a 

 number of smaller horns were secured 



741 



within it, all being controlled by a single 

 mouthpiece. As it now stands the horn 

 contains no inner megaphones. Long 



A loader which is built like a California gold-dredge and 



which can handle one cubic yard of crushed rock in a 



minute and a quarter 



A megaphone which was built to carry sound 

 without the waste of a single vibration 



iron wires have been attached, extending 

 from near the mouthpiece to beyond the 

 end of the horn. Their purpose is to 

 prevent echoing, and to purify and 

 clarify the sound. The giant mega- 

 phone measures ten feet 

 four inches across the 

 large opening and eight 

 feet in length. 



Wagon-Loader Re- 

 sembles Gold -Dredge 

 A WAGON-LOAD- 

 ING machine has 

 been brought out which 

 in appearance and opera- 

 tion is a repHca in minia- 

 ture of the huge dredges 

 used in Cahfornia and 

 Alaska for mining sur- 

 face-gold. To a chain 

 passing around two pul- 

 leys, one at either end of 

 a steel frame, small steel 

 scoops or buckets are 

 attached at regular in- 

 tervals. An electric mo- 

 tor supplies the power. 



