COJi'DlTIONS OF CONDENSATION^-. 251 



place, it will be accompanied by a great and sudden disen- 

 gagement of heat ; and until this excess of heat has 

 escaped, the newly-formed binary atoms will remain uni- 

 formly diffused, or, as it were, dissolved in the pre-existing 

 nebulous medium. 



But now mark what must happen. When radiation has 

 adequately lowered the temperature, these binary atoms will 

 precipitate ; and having precipitated, they will net remain 

 uniformly diffused, but will aggregate into JloccuU : as water, 

 precipitated from air, forms clouds. 



Concluding, then, that a nebulous mass will, in course 

 of time, resolve itself into flocculi of precipitated denser 

 matter, floating in the rarer medium from which they were 

 precipitated, let us inquire what will be the mechanical 

 results. Masses dis^^ersed through empty space, and moving 

 to their common centre of gTavity in lines determined solely 

 by their mutual attractions, will not produce any axial 

 motion in the aggregate they form. But w^hat will happen 

 with irregularly dispersed masses of irregular shapes when 

 they are suspended in a medium which is denser near 

 its central parts than near its periphery ? Their motions of 

 concentration will be subject to deviations caused by local 

 mutual attractions (which taking the whole aggregate, must 

 cancel one another) ; but they will also be subject to devia- 

 tions otherwise produced which ^vill not necessarily cancel 

 one another. Their initial movements, made in all cases 

 indirect, both by local attractions, and by the unequal pres- 

 sures of the resisting medium on their irregular faces as they 

 pass through it, will always be towards one or other side of 

 the common centre of gravity of the aggregate. What now 

 must result when a flocculus, having such oblique movement, 

 encounters in its progress a medium that is always denser 

 on the side towards the centre of gravity than on the side 

 away from it ? There must perpetually be caused a deflec- 

 tion by the difference of pressure : beyond that indirect- 



