Dr. Harems reply to Professor Olmsted. \ & 



owe their light ; and that his removal from the system would 

 simultaneously involve them in darkness, and destroy the re- 

 ciprocal attraction between them, and their satellites. This 

 is a glaring error. The reaction between the Sun and plan- 

 ets, is reciprocal, arising from a quality inseparable from 

 either, and which admits of no increase, transfer, or diminution. 



If the Sun did " communicate his attractive influence' 1 '' to the 

 other bodies in the solar system, I should be unable to say 

 why he might not communicate any other property. The 

 transmission of heat, in vacuo, is analogous to the radiation 

 of light not the reciprocal influence of gravitation. If the 

 illumination of Saturn or Uranus, could be explained with- 

 out supposing the existence of a material fluid, I grant that 

 the passage of heat in vacuo ought to admit of a similar ex- 

 planation. 



But as it is to me inconceivable, and contradictory to the 

 obvious meaning of the word, to suppose the existence of a 

 property without matter to which it may belong ; so it ap- 

 pears impossible that there can be a transfer of a property, 

 effected through a space otherwise void, without a transfer 

 of matter. 



* The following paragraph was written in opposition to the 

 hypothesis of motion, it is noticed by Professor Olmsted, as 

 if intended directly to support the materiality of heat, as the 

 reader will perceive by his remarks which I shall also quote. 



" As in order for one body or set of bodies in motion to resist 

 another body or set of bodies in the same state, the velocity 

 must be as much greater, as the weight may be less, it is incon- 

 ceivable that the particles of steam should by any force, arising 

 from their motion, impart to the piston of a steam engine the 

 wonted power ; or that the particles of air should prevent a col- 

 umn of mercury, almost infinitely heavier, from entering any 

 space in which they may be included by beating it out of the 

 theatre of their vibratory, and rotatory movements." 



Ci Has not Dr. Hare plainly fallen into a mistake here ? It 

 evidently is not heat which moves the piston of a steam-engine, 

 but it is the elastic force of steam. " But, it may be asked, is 

 not that elasticity caused by heat ?" True ; but the effect is not 

 the same thing with the cause." 



Was ever an inquiry more irrelevant ? Where have I said 

 that heat does move the piston of a steam-engine. In the 

 paragraph above quoted which gives rise to the inquiry, I 

 have only argued that motion produced among the aqueous 



