March 16, 1883.] 



SCIENCE. 



175 



range for the extent of an octave is slight. — {Comptes 

 renJiis, Nov. 22, 1882.) c. R. C. [353 



Heati 



Relation bet-ween latent heat, specific heat, 

 and volurne. — It is pointed out by Mr. Trouton 

 that the latent heat of gasification at constant pres- 

 sure of any body, divided by the product of the rela- 

 tive volume of the gas and the specific heat of the 

 body, is approximately constant. Tliis constant is 

 calculated for many substances. The only marked 

 exceptions are water and acetic acid. — {Nature, 

 xxvii.. No. 091.) c. B. P. [354 



Exception to the second la-wr of thermody- 

 namics. — An ingenious method has been devised by 

 Prof. H. T. Eddy to show that radiant heat is au ex- 

 ception to the second law of thermodynamics. The 

 method is based .upon the fact that heat is radiated, 

 not instantaneously, but with a finite velocity, and 

 consequently it is possible for occurrences to take 

 place, during the exchange of radiations between 

 two bodies, such as essentially to alter the ultimate 

 distribution of heat. If three screens, composed of 

 some perfectly reflecting material, are provided with 

 suitable apertures, and are placed parallel between 

 two radiating bodies, velocities can be communicated 

 to the screens such that radiations from the first body 

 will pass through the apertures to the second body, 

 while tlie radiations from the second body will be in- 

 tercepted, and reflected back. Thus, if the tempera- 

 ture of the first body is less than that of the second, 

 heat can be transmitted from a colder to a hotter body 

 without compensation, and without the expenditure 

 of work. 



The axiom of Clausius, that heat cannot of itself 

 pass from a colder to a hotter body, and the similar 

 axiom of Thomson, are thus only true with regard 

 to radiations, if the velocity of radiation is infinite. 



The arrangement employed by I'rof. Eddy, which 

 he calls the 'radiation siren,'' proves that we can 

 no longer regard the law of dissipation of energy of 

 universal validity, and we cannot accept tlie principle 

 of Clausius, that the entropy of the universe tends 

 to a maximum. — (Proe. Amer. phil. soc, xx. No. 

 112.) c. B. P. [355 



Electricity. 



Electric railiways. — Professor Ayrton, in a lecture 

 at the Royal institution, showed that the weight of 

 a train on an electric railway would be comparatively 

 small, because stationary engines would be used, and 

 each pair of wheels on all the cars could be used as 

 drivers. Hitherto the objection to the extension of 

 electric railways has been, that the insulation of the 

 rails used as part of the motive circuit was imper- 

 fect. Prof. Perry and the lecturer have devised au 

 arrangement by which the passing train depresses 

 a series of corrugated steel disks mounted on stands 

 some inches above the track, and thus makes a 

 carefully protected contact with the insulated main 

 cables on each side; at the same time putting a tem- 

 porary earth fault in an auxiliary wire, which records 

 at the station the progress of the train. The track 

 is divided into sections, from each of which the cur- 

 rent is cut out while a train is on the section next 

 in advance. If a train enters the section so cut out, 

 its electromotors are shunted, so as to powerfully re- 

 sist the motion of tlie train. The electric lighting 

 of the cars is kept up, in such a contingency, by the 

 automatic switching-in of Faure batteries. — (Nature, 

 Jan. 11.) J. T. [356 



Wimshurst's electrical machine. — Two circu- 

 ar glass plates 14^^ inches in diameter, and J of an 



inch apart, with 12 brass strips cemented on the 

 outside of each at equal angular intervals, rotate 

 in opposite directions on the same axis. Opposite 

 strips on the same plate are connected once in each 

 revolution by a curved metallic rod terminated with 

 brushes. Tlie electricity is collected by combs oppo- 

 site the horizontal diameter. With the instrument 

 described, under ordinary atmospheric conditions, a 

 4.J-inch spark was oljtained once in every 2J revolu- 

 tions. The only apparent exciting cause is the fric- 

 tion of the air between the plates. — {Enyineering, 

 Jan. 5.) J. T. [357 



New telephone receiver. — S. P. Thompson has 

 devised an improvement 911 the instrument of Philip 

 Reis, who utilized the sound emitted by a magne- 

 tized bar due to fluctuations in the magnetizing 

 circuit. The improvement consists in making the 

 magnetized core slender and subject to adjustable 

 tension, and attaching one end to a suitable vibrat- 

 ing plate. In one form two cores are used, one being 

 of "nickel, which contracts when magnetized; the op- 

 posite movements being used to increase the distortion 

 of the membrane. It is claimed that articulation, 

 especially of sibilants and certain other consonants, 

 is more distinct with this than with the comjuon 

 receiver. — (£^H(/(iieerm!/, Jan. 26.) J. T. [358 



Value of the Siemens unit. — E. Dorn, by a 

 modification of Weber's second method by which he 

 eliminates the influence of terrestrial magnetism, es- 

 tablishes the relation 



mm. 



S . U = .94825 X 10i» , 



sec. 



and compares this result with those of other observers 

 in this table: — 



Lorentz . . 

 Kayleigh . . 

 Kohlrausch . 

 H. F. Weber 



.9.333 

 .9413 

 .9440 

 .9550 



'Rowland 

 Dorn . . . . 

 [Ann. phys. und chein., xvii. 13.) J. t, 



iBrit. Assoc. 



from 



.9530 

 .9431 

 .9459 

 .9483 



[359 



CHEMISTRY. 



(^Aiiitlijtical.) 



Absorption apparatus for elementary analy- 

 sis. — For absorption of the prod- 

 ucts in organic analysis, C. Winkler ' 

 proposes the spiral apparatus shown 

 in the accompanying illustration. 

 It sliould be capable of holding 20 

 grms. of sulphuric acid or 15 grms. 

 of potassium hydrate solution ; and 

 it may be used to absorb either 

 water or carbonic dioxide. — 

 {Zeitschr. anal, chem., 1882, 545.) 

 C. F. M. [360 



Separation of barium from strontium or cal- 

 cium by potassium chromate. — J. Merscher- 

 zerski finds that barium chromate is soluble in 23,000 

 parts water, more soluble in acetic acid, and it has a 

 great tendency to carry down other salts from the so- 

 lution in which it is precipitated. Since strontium 

 chromate requires 840 parts water for solution, it 

 would be precipitated in a solution containing more 

 than one per cent. The author therefore concludes 

 that this method affords a convenient and sufliciently 

 accurate means for a qualitative separation; but it 

 cannot be relied upon for quantitative purposes. — 

 (Zeitec/ir.anaJ. cftem., 1882, 399.) c. F. M. [361 



1 The 

 B.A.I 



esults depend 

 = 1.0493. 



the ratio, given by Kohlrausch, 



