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Seite 227 - ... must therefore be confined to dead matter; but such apprehensions are, it is believed, groundless, or, at all events, premature. All parts of living structures are allowed to be in a state of incessant change, of decomposition and renewal. The decomposition occurring in a living membrane, while effecting osmotic propulsion, may possibly, therefore, be of a reparable kind In other respects chemical osmose appears to be an agency particularly adapted to take part in the animal economy.
Seite 351 - ... temperature, and emits heat only in another locality kept at a uniform temperature, the temperatures of these localities are proportional to the quantities of heat taken in or emitted at them in a complete cycle of the operations. To fix on a unit or degree for the numerical measurement of temperature, we may either call some definite temperature, such as that of melting ice, unity, or any number we please ; or we may choose two definite temperatures, such as that of melting ice and that of saturated...
Seite 340 - where /= .00082 for air, f= .0064 for carbonic acid, and /= — .00043 for hydrogen. No doubt the deviations from Boyle's law will be somewhat different at the higher temperature (about 15° or 16° Cent.) of the bath in our experiments, probably a little smaller for air and carbonic acid, and possibly greater for hydrogen ; but the preceding formula may express them accurately enough for the rough estimate which we are now attempting. We have, therefore, for air or carbonic acid...
Seite 146 - The application of these axioms to Heat and Expansive Power virtually involves the following definition of expansive heat : — Expansive Heat is a species of Actual Energy, the presence of which in a substance affects, and in general increases, its tendency to expand. And this definition, arrived at by induction 'from experiment and observation, is the foundation of the theory of the expansive action of heat. SECTION IV.
Seite 321 - The space enclosed by the perforated plates is 2.72 inches long, and an inch and a half in diameter, and being filled with cotton, silk, or other material more or less compressed, presents as much resistance to the passage of the air as may be desired. A tin can, d, filled with cotton - wool, and screwing to the brass casting, serves to keep the water of the bath from coming in contact with the boxwood nozzle. In the following experiments, made in order to ascertain the variations in the cooling...
Seite 339 - Section II. (10), communicated to tht Roy. Soc. Edinb., Feb. 4, 1850; Transactions, Vol. XX., p. 160. of Elastic Fluids,"* he took the first opportunity of testing it closely, afforded by our preliminary experiments on the thermal effects of air escaping through narrow passages. We are now able to give much more precise answers to the question regarding the heat of compression, and to others which rise from it, than those preliminary experiments enabled us to do.
Seite 227 - The natural excitation of osmose in the substance of the membranes or cell-walls dividing such solutions, seems therefore almost inevitable. In osmose there is, further, a remarkably direct substitution of one of the great forces of nature by its equivalent in another force — the conversion, as it may be said, of chemical affinity into mechanical power. Now what is more wanted in the theory of animal functions than a mechanism for obtaining motive power from chemical decomposition as it occurs...
Seite 321 - Another improvement was now effected by introducing a nozzle constructed of boxwood, instead of the brass one previously used. This nozzle is represented by fig. 1, Plate IV., in which aa is a brass casting which bolts upon the terminal flange of the copper piping, bb is a turned piece of boxwood screwing into the above, having two ledges for the reception of perforated brass plates, the upper plate being secured in its place by the turned boxwood cc, which is screwed into the top of the first piece....
Seite 116 - Throughout the whole of this investigation, quantities of heat, and coefficients of specific heat, are expressed, not by units of temperature in a unit of weight of water, but by equivalent quantities of mechanical power, stated in foot-pounds, according to the ratio established by Mr. JOULE'S experiments on friction (Phil. Trans. 1850) ; that is to say, 772 foot-pounds per degree of FAHR., or 1389'6 foot-pounds per Centigrade degree, applied to one pound of liquid water at atmospheric temperatures.