Cyclomathesis: Or, An Easy Introduction to the Several Branches of the Mathematics]., Volume 6

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Page 155 - ... distinctly with both eyes, the axes of both eyes are directed to that point, and meet there; and then the object appears single, though looked at with both eyes; for the optic nerves are so framed, that the correspondent parts in both eyes, lead to the same place in the brain, and give but one sensation; and the image will be twice as bright with both eyes as with one. But if the axes of both eyes be not directed to the object, that object will appear double, as the pictures in the two eyes do...
Page 240 - Thus then mall there be made two bows of colours, an interior and ftronger by one reflexion in the drops, and an exterior and fainter by two (for the light becomes fainter by every reflexion),- and their colours...
Page 155 - But if the axis of both eyes be not directed to the object, that object will appear double, as the pictures in the two eyes do not fall upon correspondent or similar parts of the retina. The best eye can hardly distinguish any object...
Page 28 - ... and the ultra-marine blue of a faint obfcure and dark red. And if they be held together in the blue homogeneal light, they will both appear blue; but the ultra-marine will appear of a ftrongly luminous and refplent blue, and the cinnaber of a faint and dark blue.
Page 71 - ... behind the mirror is greater than the object, and it has the same direction : in proportion as the object approaches the focus, the image becomes larger and more distant. These and similar results are proved by placing a lighted candle at different distances from a concave mirror. 4. An eye cannot see an image in the air except it be placed in the diverging rays ; but if the image be received on a piece of white paper, it may be seen in any position of the eye, as the rays are then reflected...
Page 43 - ... the fhadows of all bodies, held in the coloured light between the prifm and the wall, were bordered with fringes of the colour of that light in which.. they were held ; and comparing the fringes made in the feveral coloured lights, he found that thofe made in the red light were the largeft, thofe made in the violet were the leaft, and thofe made in the green were of a middle bignefs.
Page 13 - XLlT are two rays, the first of which comes from the lower part of the sun to the higher part of the image, and is refracted in the prism at K and H, and the latter comes from the higher part of the sun to the lower part of the image, and is refracted at L and I.
Page 155 - When any point of an object is seen distinctly with both eyes, the axis of both eyes are directed to that point, and meet there : and then the object appears single, though looked at with both eyes ; for the optic nerves are so framed, that the correspondent parts in both eyes lead to the same place in the brain, and give but one sensation ; and the image will be twice as bright with both eyes as with one. But- if the axes of both eyes be not directed to...
Page 42 - And hence I gather, that the Light which makes the Fringes upon the Paper is not the same Light at all distances of the Paper from the Knives, but when the Paper is held near the Knives, the Fringes are made by Light which passes by the edges of the Knives at a less distance, and is more bent than when the Paper is held at a greater distance from the Knives.
Page 239 - Eye, and thereby ftrike the fenfes with the deepeft violet Colour in that region. And in like manner the Angle SFO being equal ta the Angle P OF, or 42 deg.

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