Chai>. III.] DOWNWARD GROWTH OF THE ROOT. 
Ill 
diminish directly as the nearness of each part 
to the centre of the wheel. Therefore, gravity 
would again resume its powers over each part 
directly as the centrifugal force diminished, and 
thus should elevate the heads of the plants on 
the horizontal wheel. This observation will 
hold good, whatever may have been the degree 
of centrifugal force applied. I have not, indeed, 
any idea of the degree which actually was ap¬ 
plied ; and it is needless to mention the number 
of revolutions of the wheels in a given time, 
since their diameters are not given in either of 
the two accounts which I have seen of this most 
beautiful experiment; therefore, no correct no¬ 
tion can be formed of the degree of centrifugal 
force to which each part of the plants was sub¬ 
jected. But, as I have said, in any case the 
degree of that force must have varied in every 
part of the plants; that is, it must have de¬ 
creased on the stems, and increased on the roots, 
directly as their growth ; and when the heads of 
the stems had worked up the stream of centri¬ 
fugal force to the centre of the wheel, “ where 
they soon met,” all action of the centrifugal 
force must have ceased on them; and had they 
not turned upward at right angles to the spokes 
of the horizontal wheel, they would have gone 
