Elements of Science and Art: Being a Familiar Introduction to Natural Philosophy and Chemistry; Together with Their Application to a Variety of Elegant and Useful Arts, Τόμος 2

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F. C. and J. Rivington, 1822

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Σελίδα 394 - It is indisputably evident that a great part of every man's life must be employed in collecting materials for the exercise of genius. Invention, strictly speaking, is little more than a new combination of those images which have been previously gathered and deposited in the memory: nothing can be made of nothing: he who has laid up no materials, can produce no combination.
Σελίδα 360 - A, 11, (.', are said to be proportional, when the ratio of the first to the second is the same as that of the second to the third.
Σελίδα 397 - To make it merely natural, is a mechanical operation, to which neither genius nor taste are required ; whereas, it requires the nicest judgment to dispose the drapery, so that the folds shall have an easy communication, and gracefully follow each other, with such natural negligence as to look like the effect of chance, and at the same time show the figure under it to the utmost advantage.
Σελίδα 398 - There is one precept, however, in which I shall only be opposed by the vain, the ignorant, and the idle. I am not afraid that I shall repeat it too often. You must have no dependence on your own genius. If you have great talents, industry will improve them : if you have but moderate abilities, industry will supply their deficiency. Nothing is denied to well-directed labour : nothing is to be obtained without it.
Σελίδα 297 - ... or ammoniacum, which must be rubbed or ground till they are dissolved. Then mix the whole with a sufficient heat. Keep the glue in a phial closely stopped, and when it is to be used set the phial in boiling water.
Σελίδα 209 - ... produces leather less durable than the leather slowly formed. Besides, in the case of quick tanning by means of infusions of barks, a quantity of vegetable extractive matter is lost to the manufacturer, which might have been made to enter into the composition of his leather. These observations show, that there is some foundation for the vulgar opinion of workmen, concerning what is technically called the feeding of leather in the slow method of tanning; and, though the processes of the.art may...
Σελίδα 170 - To bleacfi cloth in this manner, it must be immersed in a slight alkaline caustic liquor, and placed in a chamber constructed over a boiler, into which is put the alkaline ley which is to be raised into Steam. After the fire has been lighted, and the cloth has remained exposed to the action of the steam for a sufficient length of time, it is taken out, and immersed in the Oxygenated Muriate of Lime, and afterwards exposed for two or three days on the grass. This operation, which is very expeditious,...
Σελίδα 257 - The manner of using the seed-lac or white varnishes is the same, except with regard to the substance used in polishing ; which, where a pure white, or great clearness of other colours is in question, should be itself white ; whereas the browner sorts of polishing dust, as being cheaper, and doing their business with greater dispatch, may be used in other cases. The pieces of work to be varnished should be placed near a fire, or in a room where there is a stove, and made perfectly dry, and then the...
Σελίδα 433 - ... the aquafortis from acting where the particles adhere, and by this means cause it to corrode the copper partially, and in the interstices only. When these particles are extremely minute and near to each other, the impression from the plate appears to the naked eye exactly like a wash of...
Σελίδα 354 - A segment of a circle is a part of a circle cut off by a straight line drawn across it. This straight line is called the chord. A segment may be either equal to, greater, or less than a semi-circle, which is a segment formed by the diameter of the circle, as CEB, and is equal to half the circle.

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