. The principles of physics. ticles would then be about 4 inches. In our atmos-phere at a hight of 210 miles, the particles are relatively so few 1 The following estimates made (by Maxwell, using a proposition formulated byClansius) for hydrogen molecules at 0°C., and under a pressure of 760 mm, mayprove Interesting: Mean velocity, 6100 feet per second. Mean path without collision, 38 ten-millionths of an inch. Collisions, 17,750 millions per second. Mass, 216,000 million million million in 1 gram. Number; 19 million iuillion million fill 1 cubic centimeter. 272 MOLECULAR DYNAMICS. that each p
. The principles of physics. ticles would then be about 4 inches. In our atmos-phere at a hight of 210 miles, the particles are relatively so few 1 The following estimates made (by Maxwell, using a proposition formulated byClansius) for hydrogen molecules at 0°C., and under a pressure of 760 mm, mayprove Interesting: Mean velocity, 6100 feet per second. Mean path without collision, 38 ten-millionths of an inch. Collisions, 17,750 millions per second. Mass, 216,000 million million million in 1 gram. Number; 19 million iuillion million fill 1 cubic centimeter. 272 MOLECULAR DYNAMICS. that each particle might travel through a uniform atmosphere ofthat density for sixty million miles without entering into collision.— Daniell. 233. Expansion and expansive force of gases. The effect of a change of temperature upon a gas may be meas-ured by noting the change in its volume when the pressure uponit is constant, or the change in its pressure when its volume isunchanged. Conversely, the changes in volume or pressure of a. .TT _ iiili FlO. 209. gas may be made to indicate changes in temperature. On thisprinciple the so-called air-thermometer is constructed. The relation between pressure and temperature of air kept at aconstant volume may be found by means of an apparatus like thatrepresented in Fig. 209. A bulb 6, whose capacity at 0° and100° C. is known, is filled with dry air. The capillary tube leadingfrom the bulb is connected to a tube T, which is connected with ABSOLUTE ZERO. 273 another tube T open to the atmosphere. The lower ends of T andT dip into a reservoir of mercury E. The bulb 6 is first sur-rounded by melting ice, and by means of the screw S the mercuryis forced to the hight h in the tube T, and the difference in levelbetween (h and h) the surfaces of Inercury in the two tubes isascertained. By adding this to the hight of the barometer at thesame moment, the total pressure to which the air in the bulb issubjected at the temperature (0° C.) of melting ice i
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Keywords: ., bookcentury1800, bookdecade1890, booksubjectphysics, bookyear1895
