256 The National Geographic Magazine 



occur ; but in weather forecasting it 

 will never be possible to attain the ac- 

 curacy acquired by astronomers in pre- 

 dicting the date of an eclipse or the 

 occurrence of celestial events. 



In this connection it is interesting to 

 note that at the time of the founding 

 of the first of the Thirteen Colonies, at 

 Jamestown, Virginia, in 1607, practi- 

 cally nothing was known of the prop- 

 erties of the air or of the methods of 

 measuring its phenomena. Today, at 

 over 200 stations in the United States, 

 Canada, and the West Indies, electric- 

 ally recording automatic instruments 

 measure and transcribe, for each mo- 

 ment of time, the temperature, the air 

 pressure, the velocity and the direction 

 of the wind, the beginning and the end- 

 ing of rainfall, the amount of precipita- 

 tion, and the duration of sunshine. 



It was not until 1643, twenty-three 

 years after the landing of the Pilgrims 

 at Plymouth Rock, that Torricelli dis- 

 covered the principle of the barometer, 

 and made it possible to measure the 

 weight of the superincumbent air at any 

 spot where the wonderful, yet simple, 

 little instrument might be placed. His 

 great teacher, Galileo, who was so 

 cruelly persecuted for teaching the 

 truth of the Copernican theory and for 

 the invention of the telescope, died with- 

 out knowing of the barometer. He 

 therefore never understood why ' * nat- 

 ure abhors a vacuum. ' ' But meteorol- 

 ogists as well as astronomers must ever 

 pay homage to his great intellect, for, 

 among many other valuable inventions, 

 he discovered the principle of the ther- 

 mometer. The data from the readings 

 of the barometer and the thermometer 

 form the foundation of meteorological 

 science. Their inventors as little ap- 

 preciated the value of their discoveries 

 as they dreamed of the great empire 

 then just rising from the mists of the 

 western seas, which should come into 

 existence and first use their instruments 

 to detect the inception of storms. 



THE RESEARCHES OF BENJAMIN 

 FRANKUN 



About one hundred years after the 

 invention of the barometer Benjamin 

 Franklin, statesman, diplomat, patriot, 

 and scientist, divined that northeast 

 storms were caused by atmospheric dis- 

 turbances located to the southwest of 

 the regions experiencing the north- 

 east winds. He compared the move- 

 ment of the air to water held in a canal 

 by a gate at the lower end. When the 

 gate is opened the water nearest it 

 moves first, then that next higher up, 

 and so on, until motion is imparted to 

 the water at the far end of the canal. 

 His simile does not explain what actu- 

 ally occurs, but it closely approaches 

 the truth. It was prophetic that this 

 idea should come to him long before 

 any one had ever seen charts that show 

 weather observations simultaneously 

 taken at a system of stations scattered 

 throughout a broad area. His theory 

 was equally as important as his act of 

 drawing the lightning from the clouds 

 and identifying it with the electricity 

 of the laboratory, but his contempora- 

 ries thought little of it and it was soon 

 forgotten. 



It will aid in understanding the cy- 

 clonic motion of storms, which will be 

 fully explained a little farther along in 

 this chapter, to learn how Franklin 

 came to reach his conclusions as to the 

 cause of the northeast winds. He had 

 arranged with his brother in Boston to 

 take observations of a lunar eclipse at 

 the same time that he himself would 

 take them in Philadelphia. Early on 

 the evening of the eclipse an unusually 

 severe northeast storm began at the 

 latter place, lasted many hours, and pre- 

 vented Franklin from getting observa- 

 tions. As the wind blew fiercely from 

 the northeast, he reasoned that of course 

 the storm came from that direction, and 

 that his brother's views in Boston also 

 were obscured. What was his surprise, a 

 few days later, to receive word that the 



