To Show The Spots In The Sun's Disk By Its Image In The Camera





Obscura.



Put the object-glass of a ten or twelve feet telescope into the

scioptric ball, and turn it about till it be directly opposite the

sun. Then place the pasteboard mentioned in page 16, in the focus of

the lens, and you will see a clear bright image of the sun, about an

inch diameter, in which the spots on the sun's surface will be exactly

described.



As this image is too bright to be seen with pleasure by the naked eye,

you may view it through a lens whose focus is at six or eight inches

distance, which, while it prevents the light from being offensive,

will, by magnifying both the image and the spot, make them appear to

greater advantage.





To Show The Pressure Of The Atmosphere To So Fill A Glass With Water That It Cannot Be Removed Without facebooktwittergoogle_plusredditpinterestlinkedinmail

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