MEASURING DEPTH OF AIR.

Pelorus Guardian and Miners' Advocate., Volume 8, Issue 28, 5 April 1907, Page 2

MEASURING DEPTH OF AIR.

One hundred and thirty-one miles is the height of the atmosphere, as measured by Professor T. J. J. See, who determines the thickness of the air envelope by noting the difference between the time of sunset and the complete disappearance of blue from the sky,

The moment at which the. blue changes into black can be observed quite easily with approximate certainty by the naked eye when the air is clear ; and by trigonometry may be ascertained the distance below the horizon of the sun at the moment of the change. By this means may be calculated the height of the smallest illuminated particles of oxygen and nitrogen, which give to the sky its blueness of tint by the reflection of the smallest wave lengths of the sun's light. The instant the change from blue to black is possibly a little dillicwlt of exact observation, but the method is not more doubtful than that based on the observation of shooting stars The shooting star method gives a result not greatly different from the vanishing blue method. The former gives the height of the atmosphere at 109 miles.