Marsh.] 114 [March 6, 



ON THE LATENT HEAT OF EXPANSION IN CONNECTION 

 WITH THE LUMINOSITY OF METEORS, ETC. 



By B. V. Marsh. 



{Bead before tlie American Philosophical Society, March 6, 1874.) 



Ill 18G3, in a paper published in Silliman's Journal (vol. xxvi. p 92), 

 I attempted to show that the luminosity of meteors is probably due to 

 the effects of latent heat. 



An abstract of my results was made by the "Luminous Meteor" Com- 

 mittee of the British Association, and published in 1864 with their 

 report. The paper was also favorably referred to by Haidinger ;* but 

 it evidently has not been accepted as furnishing a satisfactory solution 

 of the problem. 



My explanation was based upon the assumption that when air is heated 

 "under a constant pressure," the heat required to produce a given 

 elevation of temperature, in excess of that required to produce the same 

 change of temperature "under a constant volume," remains latent in the 

 expanded air. But according to the dynamical theory of heat, the most 

 of this excess is employed in lifting tlie weight of the atmosphere ; a 

 glance, however, at the tabular statement in my paper, shows that a very 



-small fraction only of this excess is actually required to produce all the 



■ effects which I attributed to it. Hence, although "latent heat of 

 expansion" seems to be generally ignored, I have always — in view of 

 the remarkable correspondence of the observed phenomena with what 

 might be expected to occur, supposing my explanation to be correct — 



; felt an assurance that it must have some foundation in truth. The fire- 

 balls of December 24th and January 2d having prompted me to re-examine 

 the question, I find this impression strongly confirmed, and therefore 

 venture again to call attention to the subject, hoping to make it appear 

 probable, not only that "latent heat of expansion" is a reality, but that 



. it plays a leading part in all the luminous phenomena of the upper 



. regions of the atmosphere. 



Tyndall, in his treatise on "Heat as a Mode of Motion" (New York, 



-* M«moire sur les relations qui existent entre les etoiles fllantes, les bolides, et les 

 essaims des m^t^orites ; par M. Haidinger, Associ(5 de rAcad(5mic — Bulletins da 

 1'A.cadeinie Royale de Bruxelles, 2e series, T. XVIL, 1884. p. 133 "M. Quetelet, dam 

 son important ouvrage sur \si Physique du GZo6e, publi(3 en 1861 (p. 5), d(5signe ces 

 couches par les noms cfatmosphere mobile ou dynamique, et d^atmosphere immobile 

 ou stable. , Les considerations publie^s par M. Benjamin V. Marsh dans le journal 

 americain du Professeui* Silliman ont grande importance relativement a I'existance de 

 deux couches atmospheriques de nature difT^rente." 



