152 the eiffel tower. 



5. Utility of the Tower. 



I. Strategic Observations. — Light can be flashed from it 

 to a distance of 39 miles, and observations taken at a dis- 

 tance somewhat less. 



II. Meteorology. — The tower will lend itself to the observa- 

 tion of the strength and changes in direction of the wind, 

 the chemical composition of the air, and the formation of 

 mist, dew, fog, rain, etc., at different altitudes, and the law 

 of the decrease of temperature. 



III. Physical Experiments. — Falling bodies and resistance 

 of the air, oscillations of pendulum, electric phenomena. 



rV. Astronomical Observations. — This point is doubtful, 

 as one cannot make sure that the tower will have only a 

 motion of translation and no rotary motion. But it may be 

 useful for spectroscopic work and researches in atmospheric 

 refraction, as it rises above the ordinary level of fog and 

 dust, and sometimes even above the clouds. 



But after all, the great utility of the tower is the lesson it 

 affords in working with iron. 



