8 Tendency of Elastic Fluids to Diffusion. 



of Siberia, I have learnt that M. Lowitz has also analysed 

 this substance. I am ignorant of the exact proportions of 

 its ingredients, according to his experiments, but if I may 

 judge from the note relative to this subject which appeared 

 in the Journal de Physique, his results were nearly the same 

 with mine; for he announces that he found it to contain 

 more than half its weight of o.xidc of chrome, together 

 with iron, alumine, and a little silica. 



II. On the Tendency of Elastic Fluids to Diffusion thwjgh 

 each oilier. By John Dalton*. 



In an early period of pneumatic chemistry it was disco- 

 vered that clastic fluids of different specific gravities being 

 once diffused through each other, do not of themselves se- 

 parate, by long standing, in such manner as that the hea- 

 viest is found in the lowest place; but, on the contrary, 

 remain in a state of uniform and equal diffusion. 



Dr. Priestley has given us a section on this subject [vide 

 Experiments and Observations, &c. abridged, vol.ii. p. 441), 

 in which lie has proved the fact above mentioned in a sa- 

 tisfactory manner; and every one's experience since, as 

 far as I know, has coincided with his conclusions. He 

 has not offered any conjecture concerning the cause of this 

 deviation from the law observed by inelastic fluids ; but he 

 suggests, that " if two kinds of air of verv different specific 

 gravities were put into the same vessel, with very great care, 

 without the least agitation that might mix or blend them 

 together, they might continue separate, as with the same 

 care wine and water may be made to do." 



'I'he ditcrminution of this point, which seems at first 

 view but a trivial one, is of considerable importance; as 

 from it we may obtain a striking trait, either of the agree- 

 ment or disagreement of elastic and inelastic fluids in their 

 mutual action on each other. 



It is th^TCiorc the subject of the following experiments 

 to ascertain whether two elastic fluids, brought into coniuc', 



• From M'.r-chcikr Tranf^aciions, fecond jei'icJj vol. i, 



couhi 



