The American journal of the medical sciences (1827)
[Thorofare, N.J., etc.] Charles B. Slack [etc.] · leaf 449
at the same time, and the distance at which they are centred read off on the holders, at c.1 The cylindrical lenses can be readily rotated, and the direction of the axis read off on the frame. The bar m is graduated in fractions of an inch commencing with the posterior surface of the holders. The… … opening in its centre two and a half inches in diameter, the lower half of which is graduated in degrees to correspond to that upon the semicircles. Behind the circular opening fits a piece of ground glass, which, when turned toward the light gives an illuminated background. The plate is designed…
Medicine
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