Encyclopædia metropolitana; or, System of universal knowledge, Volume 161851 |
Common terms and phrases
acid acted action added allowed appear applied beautiful become blue bromine camera chemical chloride cloth coating colour combination complete considerable containing copper copy covered daguerreotype dark darkened described developed direct dissolved distilled water drawing dried effect employed Engravings equally experiments exposed exposure fixed fluid ounce formed frame give glass gold grains half heat HISTORY hydriodic hyposulphite impression inches influence intensity iodide iodine iron John leaves less light liquid manner means mercury metal method minutes muriate nature necessary negative nitrate of silver object observed obtained operation ounce paper passing perfect photographic picture piece plate portion positive potash potassium prepared present Price produced pure quantity rays remain remarkable removed rendered salt sensibility sensitive sheet side soda solution sufficient sunshine surface taken tint tion vapour washed yellow
Popular passages
Page 46 - The copy of a painting or the profile, immediately after being taken, must be kept in an obscure place ; it may, indeed, be examined in the shade, but in this case the exposure should be only for a few minutes ; by the Light of candles or lamps, as commonly employed, it is not sensibly affected.
Page 46 - When the shadow of any figure is thrown upon the prepared surface, the part concealed by it remains white, and the other parts speedily become dark.
Page 47 - I dip it into a weak solution of common salt, and wipe it dry, by which the salt is uniformly distributed throughout its substance. I then spread a solution of nitrate of silver on one surface only, and dry it at the fire. The solution should not be saturated, but six or eight times diluted with water. When dry, the paper is fit for use.
Page 47 - The images formed by means of a camera obscura have been found to be too faint to produce, in any moderate time, an effect upon the nitrate of silver.
Page 111 - ... of the total light reflected, and in short exposures is such as would easily escape notice. Nevertheless, if a slip of this paper be held for only four or five seconds in the sun (the effect of which is quite imperceptible to the eye), and when withdrawn into the shade be washed over with the ferrosesquicyanate of potash, a considerable deposit of Prussian blue takes place on the part sunned, and none whatever on the rest; so that on washing the whole with water, a pretty strong blue impression...
Page 3 - Biblical Cyclopaedia; or, Dictionary of Eastern Antiquities, Geography, Natural History, Sacred Annals and Biography, Theology, and Biblical Literature, Illustrative of the Old and New Testaments.
Page 116 - I have before me a specimen of paper so treated in which the effect of thirty seconds' exposure to sunshine was quite invisible at first, and which is now of so intense a purple as may well be called black, while the unsunned portion has acquired comparatively but a very slight brown. And (which is not a little remarkable, and indicates that in the time of exposure mentioned the maximum of effect was attained) other portions of the same paper exposed in graduated progression for longer times, viz.
Page 48 - ... seems quite extinct. But if it is again washed with a liberal quantity of the solution of silver, it becomes again sensible to light, and even more so than it was at first. In this way...
Page 4 - It is so natural," says this experimentalist, "to associate the idea of labour with great complexity and elaborate detail of execution, that one is more struck at seeing the thousand florets of an Agrostis depicted with all its capillary branchlets, (and so accurately, that none of all this multitude shall want its little bivalve calyx, requiring to be examined through a lens), than one is by the picture of the large and simple leaf of an oak or a chesnut.
Page 48 - ... that the attempt to give it sensibility has been carried too far. The object is, to approach to this condition as near as possible without reaching it; so that the substance may be in a state ready to yield to the slightest extraneous force...