. Nature . surrounded by trees, so the ends of the ttace are cut oftsharply by shadows. With the alteration of declination of the sun, the light. entering the camera is reflected from different portions ofthe sphere, and an alteration of the position of the focusresults. This may be corrected in three ways : by moving NATURE {Feb. 5, 1885 (1) the paper, (2) the lens, or (3) the sphere. In the pre-sent apparatus the first method has been adopted, andnow the camera is about twice as long as it was in a consequence the circular image is enlarged, and thelight therefore weakened, and that
. Nature . surrounded by trees, so the ends of the ttace are cut oftsharply by shadows. With the alteration of declination of the sun, the light. entering the camera is reflected from different portions ofthe sphere, and an alteration of the position of the focusresults. This may be corrected in three ways : by moving NATURE {Feb. 5, 1885 (1) the paper, (2) the lens, or (3) the sphere. In the pre-sent apparatus the first method has been adopted, andnow the camera is about twice as long as it was in a consequence the circular image is enlarged, and thelight therefore weakened, and that at a time of year whenit can least be spared. If the focus is altered by movingthe lens, the winter circle is small and the summer circleis much larger. This would perhaps be too much to theadvantage of the winter sun. If, however, the lens andpaper are maintained at a constant distance, and thesphere alone moved, the circles are more nearly of thesame diameter throughout the year, the winter one stillremaining the smallest. This seems, therefore, to be themost advantageous arrangement, and the one that will beadopted in future. It may be
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Keywords: ., bookcentury1800, booksubjectnaturalhistory, booksubjectscience
