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THE NATIONAL GEOGRAPHIC MAGAZINE 



© Eastman Kodak Company 

 A MOSAIC MAP OF ROCHESTER, N. Y., A CITY OF 300,000 INHABITANTS, MADE FROM 

 AN ELEVATION OF IO.OOO FFFT IN A SINGES FLIGHT 



The map is made from prints of eighty separate negatives, in the form of a single strip 

 of film ten inches wide and seventy-five feet long, all taken in the course of a single flight of 

 one hour and twenty minutes. Such an accomplishment suggests the great value of this form 

 of aerial photography in map-making over otherwise inaccessible territory. 



would have to wear gas masks and gog- 

 gles in order to protect itself. Two hos- 

 tile airplanes could accomplish this effect. 

 I f it were desired to use mustard gas, 70 

 tons of this very poisonous element 

 would be necessary. 



The greatest precautions would have 

 to be taken against such an attack. As a 

 matter of fact, it would cause the evacu- 

 ation of the whole city, paralyze its means 



of transportation, and result in its virtual 

 extinction as a port. If phosgene gas 

 were used, 200 tons would be required to 

 be dropped every eight days. This is a 

 very deadly gas and will have almost im- 

 mediate effect, and will kill every man, 

 woman, and child not carefully protected 

 against it. 



Gases even more deadly than this are 

 being experimented with and considered 



