July 5, 1895.] 



SCIENCE. 



25 



proportion of the difference between the 

 final range between the boiler and atmos- 

 phere or other lower limit of temperature 

 and the range between the firebox temper- 

 ature and the same lower limit. If the 

 absolute furnace temperature is 2000° C, 

 boiler temperature 500° C, and condenser 

 temperature 350°, for example, the avail- 

 ability of the heat generated by combustion 

 is reduced at the first step from (2000-350) 

 /2000 = 0.825 to (500-350) /500 = 0.30 ; 

 even though the most perfect of thermo- 

 dynamic engines is employed. 



" But though the second law is scientific- 

 ally precise and incontrovertible, it is hard 

 at first to realize how and why it can be 

 true that the temperature which exists in 

 bodies so entirely controls its availability 

 or working power." This the author pro- 

 ceeds to explain by reference to illustrations 

 in other fields of energetics. The deduc- 

 tion follows : 



" The transferable portion of heat is to 

 the whole heat as the available difference 

 of temperature is to the whole temperature 

 above absolute zero. Hence the efiiciency 

 of transfer is equal to the ratio of the avail- 

 able difference of temperature to the max- 

 imum absolute temperature." 



This is Professor Lodge's enunciation of 

 the second law of thermodynamics. It fol- 

 lows that "A working substance above aver- 

 age pressure has some available mechanical 

 energy ; a working substance below average 

 temperature has some available thermal 

 energy, but a substance at average pres- 

 sui'e and temperature has no available en- 

 ergy." 



" The second law of thermodynamics re- 

 lates to the utilization of heat energy as 

 heat, i. e., as irregular and uncontrollable 

 molecular motion. If, by any means, mo- 

 lecular motion could be taken under con- 

 trol, it would cease to be heat — the second 

 law of thermodynamics would not apply to 

 it — and a much greater portion of its energy 



might become available." Thus "Animals 

 do not turn their food energy into heat, but 

 utilize it direct. Thej' are not heat engines. 

 If they were, they would be miserably in- 

 efBcient because of their low temperature ; 

 but they are chemical engines, analogous to 

 the electric battery and are marvellously 

 eflBcient." 



A working substance, for use in any 

 heat engine, must have the following quali- 

 fications to insure efficiency : 



1. It must have great capacity for heat. 



2. It must be able to sustain high tem- 

 perature. 



By utilizing the whole difference of tem- 

 perature between the furnace and the sur- 

 rounding bodies, anj^ heat engine, as, for ex- 

 ample, the gas engine, is seen to involve, 

 according to the laws of thermodynamics, 

 a possibility of raising the efiiciency of the 

 heat engine, "not five or six per cent., 

 which is almost all the present difference 

 between the best steam engines and the 

 worst, but to a revolutionary change of 

 fifty or sixty per cent ; no drop of tempera- 

 ture being permitted from furnace to every- 

 day temperature, without delivering up its 

 due equivalent of motive power." 



R. H. T. 



SOCIETIES AND ACADESIIES. 



ALABAMA INDUSTRIAL AND SCIENTIFIC 



SOCIETY. 



The annual meeting of this Society was 

 held in Birmingham on the 8th instant. 

 The officers elected for the ensuing year are 

 Mr. Thomas Seddon, President, and Messrs. 

 E. A. Uehling and C. E. Bowron, Vice- 

 Presidents; Messrs. Eugene A. Smith and 

 Henry McCalley were continued as Secre- 

 tary and Treasurer respectively. The re- 

 tiring President, Dr. Wm. B. Phillips, in 

 his adch-ess before the Society, gave some 

 particulars of the experiments conducted 

 by him in Bessemer for the concentration 

 of the Red Mountain (Clinton) ores. This 



