This historic book may have numerous typos and missing text. Purchasers can download a free scanned copy of the original book (without typos) from the publisher. Not indexed. Not illustrated. 1921 Excerpt: ...taken during the War there were numerous marks which might have either a positive or a negative solidity, i.e. they might have been either projections above the ground, such as machine-gun emplacements, or depressions, such as shell holes. This could only be determined by the shadows cast, and the direction of the sun's rays was always marked on such photographs. Thus A is a projection and B a depression. In judging very short distances, two eyes are an enormous advantage. Try to thread a needle with one eye closed. At rather longer distances this may be demonstrated by looking at a wall between which and the observer an e object. such as the wire of an electric Fl-5Shadowslamp, is suspended. Using one eye only and avoiding looking at the point of attachment to the ceiling we will judge its distance from the wall very imperfectly, but with both eyes we can make an accurate estimation. At long distances numerous external factors come into play. Perspective, light and shade and atmospheric conditions are of importance. Thus qvisibilityq may be good or bad, and will influence our judgments. At sea, where the surface is perfectly flat and the gradations of illumination change uniformly with distance, the untrained eye commits the grossest errors. The proximity of an object of known size frequently supplies a scale against which to measure the size and consequently the distance of unknown distant objects. The faculty of judging distances is poorly developed in the average man. A traine'd soldier or a big game shot can make incomparably more accurate estimations of distances for rifle fire than the novice. The same thing occurs with the expert golfer for certain distances. 5. The Stereoscope. The combination of two slightly dissimilar pictures to...This historic book may have numerous typos and missing text. Purchasers can download a free scanned copy of the original book (without typos) from the publisher. Not indexed.
|Title||:||An Introduction to Biophysics|
|Author||:||David Burns, MD, PhD|
|Publisher||:||Rarebooksclub.com - 2012-05-18|