The Popular Science Monthly 

 for July 



Are mine fields a real defense against 

 submarines? Ships are being torpedoed every 

 day in the mined English Channel and in 

 harbors seemingly impregnable because of the 

 extensive mine fields that guard the entrance. 

 Could this happen in New York Harbor? 



The Mine That Hears 



One of the most prominent of our engineers 

 has invented a system to destroy instantly 

 any submarine ichich might attempt to pene- 

 trate into our harbors. He describes this 

 wonderful invention in the Jidy Popular 

 Science Monthly. 



How to Camp 



Are you going camping this summer? 

 Next month will appear an article on this 

 subject which ivill give new ideas to even the 

 most seasoned camper. 



What Sailors Don't Know 

 About SaiHng 



Most yachtsmen think that they know how 

 to sail a boat. They don't. Professor H. A. 

 Everett, of Johns Hopkins University has 

 analyzed the science of sailing a boat, and 

 shojvs in the July issue just why most men 

 handle their boats badly. 



The Voice Typewriter; Talk and 

 It Writes 



Other features are: " Automobile Repair 



Kinks,'' "A Typewriter That Obeys the 



Human Voice," "^4 New Armor Protection 



for Ships," and — but ivhy continue? There 



are three hundred more. 



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