Page:Encyclopædia Britannica, Ninth Edition, v. 11.djvu/616

Rh 582 HEAT &quot; linear &quot; diffusion of heat, as Fourier calls the diffusion of heat when the isothermal surfaces are parallel planes. The curves of the following diagram and Tables A. B, and C show in a practically useful way the result in the course of the times noted, of from fractions of a second to thousands of millions of years, of linear diffusion of two different qualities in an infinite line from an initial con dition in which there is sudden transition from one quality to the other, in the thoroughly practical cases specified in the accompanying explanations. No. 1. No. 2. 1 i X ^ X ~^, ^ X x X 1 X X / y. Eq v = prove xii. ( is foi from y nation of &amp;lt;r No. 2 is - X*jKt th. App. ve No. 1 uadrature fvdx. X /I / &amp;lt; t / / / - 2(0* d in Ma 27). Cui md by c (2) thus = const, x / / ! I FIG. 11. Diagram of Diffusion. Curve No. 1 shows temperature ; or quantity of substance in solution ; or potential in the conductor of a submarine cable through which electricity is diffusing. Curve No. 2 shows rate per unit of distance of variation of the temperature, or of the quantity of sub stance in solution. Vertical ordinates are actual distances through the medium. Horizontal ordinates represent temperature or quan tity of diffusing substances in No. 1 curve, and rate of variation of temperature or of diffusing substance or of electric potential in No. 2 curve. Diffusions. Table A. Substance. Carbonic acid through air Heat through hydrogen copper iron air underground strata wood Common salt through water .. Time in Seconds from the commencement of the Diffusion until the Condition represented by the Curves on the Actual Scale (6=2 Centimetres) is reached. 6 &quot;97 seconds. 89 of a second. 93 5 5 seconds. 6-25 ,, 100-0 770 87150 Electricity through Suez-Aden cable... 1 087 x 10~ 16 of a second (Vden-Bombay cable. .JO 739 x 10~ 16 Persian Gulf cable Atlantic cable French Atlantic cable. Direct U.S. cable... 0-635xlO- 16 0-440xlO- 16 396xlO- 16 0-340xlO- 16 Diffusions (Secular}. Table B. Substance. Time in Years from the commencement of the Diffu sion until the Condition represented by the Curves on the Scale of 6=20 Kilometres, or 1,000,000 times the Actual Scale, is reached. Carbonic acid through air 1 220,000 years. Heat through hydrogen 28,000 ,, ,, copper 29,000 ,, ,, iron 174,000 ,,, , air 198,000 ,, ,, underground strata 2 ..., , wood 317,000 ,, 24,700,000 ,, Common salt through water 3 2,760,000,000 ,, 1 Instructive as to the proportion of carbonic acid in air at different heights, proving its approximate uniformity due to convection, not to diffusion. 2 Instructive as to geological theories respecting terrestrial temperature. Table C. Name of Cable. Time in Seconds from the commencement of the Diffusion until the Condition represented by the Curves on the Scale of 6=1000 Nautical Miles, or 92,615,000 times the Actual Scale, is reached. Suez- Aden 932 of a second. Aden-13ombay. G 634 ,,. Persian Gulf 0-545 ,, Atlantic 0-377 ,, French Atlantic 0-339 ,, Direct United States 0-292 ,, 83. The following tables contain useful information regarding various thermal properties of matter. Every known property of a piece of matter, except its gravity and its inertia, varies with variation of temperature. For further information respecting the effect of variation of temperature in causing changes in properties of matter reference is made to the articles ELASTICITY, ELECTRICITY, MAGNETISM, LIGHT, MATTER (PROPERTIES OF), &c. TABLE I. Linear Expansions of Solids. 1 Name. Mean Expansion per degree C. through Range stated Range. 2 Authority. Silver 00002120 to 100 Muschenbrock. 1910 100 Kupffer. , 1943 100 Matthiessen. Thallium 3021 40 1 Sulphur, Sicily 6413 40 Fizcau. Selenium, cast 3G80 40 1 Tellurium, 1C75 40 } Lead 2799 to 100 Matthiessen. n 2924 40 Fizcau. 1156 s to 100 Borda. 1190 100 ( Calvcrt, Johnson, ^ and Lowe. Steel, annealed 1220 100 Muschenbrock. French cast, &amp;gt; tempered.. ) 1322 40 1 French cast, ) annealed... ) 1101 40 VFizeau. English cast, annealed... ) 1095 40 } Steel, soft 103 N ii H2 to 100 (_ Calvert, Johnson, f and Lowe. Cobalt, red by H. ) compressed .. j 1236 40 1 Fizeau. Nickel, red by H. ) compressed f n 1279 40 ] 1 Abridged from Clarke s Constants of Nature. table, the corresponding statement is to be understood as applying through a small range on either side of the number stated.
 * Instructive as to theories respecting the saltness of the sea.
 * Where only one number is given for the range in this and the following