Encyclopaedia Americana: a popular dictionary of arts, sciences, literature, history, politics and biography, brought down to the present time : including a copious collection of original articles in American biography : on the basis of the seventh edition of the German Conversations-Lexicon (Volume 13).
- Date:
- 1830-33
Licence: Public Domain Mark
Credit: Encyclopaedia Americana: a popular dictionary of arts, sciences, literature, history, politics and biography, brought down to the present time : including a copious collection of original articles in American biography : on the basis of the seventh edition of the German Conversations-Lexicon (Volume 13). Source: Wellcome Collection.
Provider: This material has been provided by the National Library of Medicine (U.S.), through the Medical Heritage Library. The original may be consulted at the National Library of Medicine (U.S.)
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![degree as to make the machine run down in a minute or two; whereas, from the resistance opposed by the pallets, it is kept going for twenty-four or thirty hours, for a week or a month, or even for twelve months. In the clocks or watches, how- ever, which, as a matter of curiosity, have been made to go so long, it was not possi- ble to have an accurate measure of time. (For the historical matter connected with this subject, see Clock.) Watelet, Claude Henry ; a French writer of eminence on the fine arts and the belles-lettres. He held the office of a receiver-general of the finances, was a member of the French academy, and of several foreign learned societies, and died at Paris, in 1786, aged sixty-eight. He published, in 1760, a poem Sur VArt de peindre, and was the author of several other works, the most im{)ortant of which is the Dictionary of Painting, Sculpture and Engi-aving, fomiing part of the En- cyclopidie Mtthodique. Water. The composition of this fluid has been fully demonstrated both from anal- ysis and synthesis. It is found that when hydrogen gas is burnt (an operation in which oxygen is combined with it), water is formed, and is the only sensible product. This is the proof by synthesis. On the other hand, when water is acted on by substances capable of attracthig oxygen, these are oxidated, the water disappears, and hydrogen gas is evolved. The pro- portions of these elements in water are as follows: one volume of oxygen to two volumes of hydrogen ; or, by weight, eight parts oxygen to one of hydrogen. Water is a transparent and colorless liquid, des- titute of smell, and nearly without taste. It refracts light powerfully. When its in- ternal movements are prevented, it is a very slow conductor of heat, and an im- perfect conductor of electricity. It is al- most incompressible, a pressure equal to 2000 atmospheres occasioning a diminu- tion of only one ninth of its bulk. Water being the substance most easily procured in eveiy part of the earth in a state of purity, it has been chosen, by universal consent, to represent the unit of the spe- cific gravity of all solid and liquid bodies. When we say the specific gravity of a body is two, we mean that it weighs twice as much as the' same volume of water would do. Now, a cubic foot of water, at the temperature of G0° Fahr., and when the barometer stands at 30 inches, weighs 908.217 avoirdupois ounces, which is on- ly 1.783 ounces less than 1000. Hence, if we know the specific giavity of a body, VOL. XIII. 8 we have very nearly the weight of a cu- bic foot of it in avoirdupois ounces. 100 cubic inches of air at 60° Fahr., when the barometer stands at 30 inches, weigh 31.144G grains. Hence it follows that wa- ter, at that tempci-ature and pressure, is 810.734 times heavier than air. Water passes to the solid state at 32° Fahr. When it shoots into ice, it fomis, in the first place, a prism, not very regular in shape, but very long. From this primary prism other smaller ones shoot out on both sides, and always at angles of 60° and 120°. Hail is always crystallized in the form of two six-sided ])yramids ap- plied base to base. Ice has been observed in crystals having the form of a rhom- boid of 120° and 60°. In taking the solid form, water undergoes an enlargement of volume from eight parts to nine ; and this expansion even takes place previous to the congelation, during the reduction of tem- perature for six or eight degi-ees, the greatest density of water being about 40° Fahr. In the act of freezing, too, the greater part of the air, which the water holds loosely dissolved, is expelled. Elec- tricity is also rendered sensible in its con- gelation. Water passes into vapor when exposed to the atmosphere at any natural temperature, and even ice evaporates, as is proved by its losing weight when sus- pended in the air. The transition into vapor is promoted by heat: at 212°, under a medium atmospheric pressure, water boils. (See Steam.) Water absorbs the aerial fluids, but in quantities very different, ac- cording to the force of attraction which it' exerts towards them. Of some of the acid gases it absorbs many times its own vol- ume ; of others, the quantity is so inc«;n- siderable as not to be very perceptible, unless ascertained by an aj)paratus pecu- liarly adapted to show the result. The quantities absorbed are greater as the temperature is low, down to freezing. They are also augmented by pressure. 100 cubic inches of recently-boiled water, at the mean temperature and pressure, absorb of Sulphureted hydrogen, 100 cubic inches. Carbonic acid, 100 Nitrous oxide, 100 Olefiant gas, 12.5 Oxygen, 3.7 « Carbonic oxide, 1.56 Nitrogen, 1.56 Hydrogen, • l.itJ All water which has been exposed to ihe atmosphere (as spring and river water) co: tains a portion of air, Ironi which it](https://iiif.wellcomecollection.org/image/b21136828_0089.jp2/full/800%2C/0/default.jpg)
