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PHYSICS, PROGRESS OF,. IN 1891. 



half as much wind as the one just an octave below 

 it, but it actually requires more than this propor- 

 tion. An organ pipe has 1,000 to 6,000 times the 

 energy of a tuning-fork. One millionth of a horse- 

 power would maintain a fork in ordinary vibra- 

 tion, and one tenth would enable it to be heard 

 200 feet, 



Timbre. Prof. Voight (Gottingen Royal Soci- 

 ety, May, 1890) has endeavored to reconcile the 

 results of Helmholtz and Koenig. (See " Annual 

 Cyclopedia," 1890, pp. 712, 713). 



Pkonautography. Dr. Pringsheim, of Berlin 

 (" Naturwissenschaf tliche Rundschau"), has at- 

 tempted to settle by physical means the long- 

 vexed question of the position of the French 

 accent. Two-syllabled words were spoken by 

 Frenchmen into a Koenig-Scott phonautograph, 

 and the resulting curves were compared with a 

 parallel tuning-fork curve. The result proved 

 that the vowels were of equal length and strength, 

 though this varied slightly with the position of 

 the word in the sentence. 



Heat. Mechanical Equivalent. This has 

 been redetermined by Constantin Miculesco 

 (Paris Academy of Sciences, June 8) by a method 

 similar to Joule's the production of heat in a 

 calorimeter by friction, In Joule's experiments 

 the total work done was small, hence the deter- 

 mination took a long time, and various difficult 

 corrections had to be made. Miculesco used a 

 1 -horse-power electro-motor to supply the work, 

 and a cylindrical calorimeter whose axis was co- 

 incident with that of the motor shaft. The mean 

 of 31 accordant measurements gave 426 - 7 kilo- 

 grammetres as the mechanical equivalent of a 

 calorie, or, in English units, J = 777'7. 



Specific Heat. Prof Pfaundler (Vienna " Be- 

 richte," April 9). in determining specific heats by 

 Joule's law, obviates difference of conductivity 

 through the liquid by using glass spirals filled 

 with mercury placed in a Wheatstone's bridge, 

 to control the ratio of resistance during the 

 flowing of the current. Prof. W. Ramsay and 

 E. P. Perman (London Royal Society), in experi- 

 ments' on the specific heat of ether, conclude 

 that, either at constant volume or at constant 

 pressure, it decreases to a limiting value as the 

 temperature rises, and then increases ; and that 

 the smaller the volume the more rapid the 

 change. 



Fusion and Solidification. Person concluded 

 that the heat of fusion of all bodies becomes nil 

 at 160. But Prof. S. U. Pickering (London 

 Royal Society Dec. 11, 1890) notes that Person 

 determined heat capacities in the liquid and solid 

 state at any convenient temperature, whereas 

 they depend largely on the temperature. Pick- 

 ering finds the temperatures of recrystallization 

 of four substances as follow, thus disproving 

 Person's law : 



Sulphuric acid, -300 



Monohydratcd sulphuric acid 1 11 



Hydrated calewna nitrato 234 



Naphthalene - 214 J 



In examining benzine it was found that the 

 heat capacity of the solid was greater than that 

 of the liquid. This phenomenon is due probably 

 to incipient fusion below the temperature of true 

 fusion. Carl Barus (" American Journal of 

 Science." August) discards optical and other 

 methods for obtaining fusion points, and employs 



volume changes as his criteria. He concludes 

 that if, under proper thermometric conditions, 

 pressure alone can solidify a liquid, it can also, 

 under proper solutional conditions, induce crys- 

 tallization or deposition of the dissolved solid. 

 R. W. Wood, Jr. (" American Journal of Science/' 

 January), found, on compressing ice by a press- 

 ure of 4 atmospheres, that a small cylinder of 

 clear ice spurted from an aperture, as in former 

 similar experiments. In a Vessel with no ap- 

 erture ice was subjected to a pressure of 20 tons 

 to the square inch without liquefying it, as 

 proved by the position of leaden bullets in the 

 mass. Fine jets of spray, however, issued in all 

 directions. He therefore questions any theory 

 that supposes a glacier to float, as it were, on a 

 layer of pressure-water. 



Recalescence (" Annual Cyclopedia," 1889, p 

 694). F. J. Smith (" Philosophical Magazine," 

 May) describes some new methods of investi- 

 gating recalescence points in steel and iron. 

 His experiments show that the change of form 

 in the metal occurs simultaneously with its 

 change of temperature. By fastening the wire 

 under observation to a sort of mechanical tele- 

 phone with mica disk, a sharp, crackling sound 

 was heard at the recalescence points. Placing 

 the wire in a magnetic field did not affect any 

 of the results. 



Thermal Properties of Hard Rubber. This 

 substance has been known for some time to 

 possess a large co-efficient of expansion and re 

 markable diathermaneity. Prof. A. M. Mayer 

 (" American Journal of Science." January) has 

 investigated both properties minutely. He 

 finds that between and 18 C. the linear ex- 

 pansion coefficient is '0000636, and that the cubi- 

 cal expansion formula is Vt = V (1 + -000182t 4- 

 00000025r 2 ). A plate | millimetre thick trans- 

 mits 32 per cent, of the incident heat from 

 a Locatelli lamp, and 24 per cent, of solar heat. 

 The index of refraction is 1'568 nearly as great 

 as that of flint glass. 



Very Low Temperatures. Prof. Pictet. of 

 Geneva, has established at Berlin what he calls 

 a " laboratoire a basses temperatures," where 

 special refrigerating machinery keeps objects 

 for any length of time at any desired tempera- 

 ture between 20 and 200 C. The purpose 

 of the laboratory is commercial, and it has 

 chiefly been occupied in the purification, by 

 crystallization, of glycerin, chloroform, ether, 

 and alcoholic liquors, but in these processes 

 many surprising scientific facts have already 

 been brought to light. For instance, it has been 

 shown that so-called " non-conducting " material 

 does not much affect the passage of heat into a 

 body below 100 C. In Prof. Pictet's words 

 ('' Nature," Nov. 12) : " The slow oscillations of 

 matter, which constitute the lowest degrees of 

 heat, pass more readily through the obstruction 

 of a so-called non-conductor than those corre- 

 sponding to a higher temperature : just as the 

 less intense undulation? of the red light are 

 better able to penetrate clouds of dust or vapor 

 than those of blue." A covering of cotton-wool 

 18 inches thick has almost no appreciable effect 

 on the rise of temperature of a substance from 

 135 to 100 C. It thus becomes more diffi- 

 cult to withdraw heat from a body the colder it 

 gets, and Prof. Pictet judges that the lowest 



