Scientific Dialogues: Intended for the Instruction and Entertainment of Young People, Inwich the First Principles of Natural and Experimental Philosophy are Fully Explained. Vol. II, IV-VI.
J. Johnson, 1809
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angle appear attract body bring brought called candle cause centre Charles colours comes concave mirror CONVERSATION convex convex lens course dark diameter direction distinct diverge divide double earth effect electricity equal experiment explain eye-glass fall farther feet figure flow focal distance focus formed glass greater half heat hole humours inches incident inverted iron James kind larger lens less look looking-glass magnet magnified means meet middle minutes move natural nearer needle object opposite optics painted parallel particles pass perpendicular person picture piece placed Plate poles proceed produced proportion radius rays of light reason reflected refraction represent retina seen shilling side sight single spectator stance stand steel Suppose surface telescope thing throw tube Tutor
Page 78 - Seasons return, but not to me returns Day, or the sweet approach of ev'n or morn, Or sight of vernal bloom, or summer's rose, Or flocks or herds or human face divine ; But cloud instead, and ever-during dark Surrounds me, from the cheerful ways of men Cut off, and for the book of knowledge fair Presented with an universal blank Of nature's works, to me expung'd and ras'd, And wisdom at one entrance quite shut out.
Page 7 - How distant some of these nocturnal suns ! So distant (says the sage) 'twere not absurd To doubt, if beams, set out at nature's birth, Are yet arriv'd at this so foreign world ; Though nothing half so rapid as their flight.
Page 107 - ... as the angle of reflection is always equal to the angle of incidence, the image for any point can be seen only in the reflected ray prolonged.
Page 164 - Meantime, refracted from yon eastern cloud, Bestriding earth, the grand ethereal bow Shoots up immense; and every hue unfolds, In fair proportion, running from the red To where the violet fades into the sky.
Page 170 - Died in the fainting Violet away. These, when the clouds distil the rosy shower, Shine out distinct adown the watery bow ; While o'er our heads the dewy vision bends Delightful, melting on the fields beneath. Myriads of mingling dyes from these result, And myriads still remain ; infinite source Of beauty, ever blushing, ever new. Did ever poet image aught so fair, Dreaming in whispering groves, by the hoarse brook; Or prophet, to whose rapture heaven descends...
Page 185 - Yes; the three glasses next the eye baving their focal distances equal, the magnifying power is found by dividing the focal distance of the object-glass by the focal distance of one of. the eye-glasses.
Page 47 - A lens is glass ground into such a form, as to collect or disperse the rays of light which pass through it. These are of different shapes, and from thence receive different names.