254 The Rev. Mr. Keith on the [Aprit, 
wheel’s axis, or otherwise ; and if otherwise, then we are not 
told any thing with respect to the degree of its deviation, or how 
it was affected by the increased or diminished velocity of the 
wheel; all which seems to be absolutely indispensable to 
Mr. Knight’s conclusion ; for if the velocity had been such as to 
counteract the force of gravitation completely, then, upon Mr. 
Knight’s principles, it is evident, that the radicle ought to have 
been protruded, not merely outwards and downwards, but hori- 
zontally ; and not yet merely horizontally, but in the direction of 
a tangent to the orbit of the bean, like the drops of water that 
flew off from the nm of Mr. Knight’s main wheel; or (to take a 
more familiar example), like the drops of water that fly off from 
the tags of atwirled mop. It ought, therefore, to have been 
. making approaches to this direction according to the degree of 
velocity with which the wheel’s motion was accelerated. Wilt 
it be said that the resistance of the air prevented it from 
approachin®, or from assuming that direction? Then the 
resistance of the air ought, for the very same reason, to have 
acted upon the radicles of the beans that were fixed to the 
eircumference of the vertical wheel, and to have affected their 
direction also. But of this we find not the slightest intimation ; 
and if it had even done so, there-is no reason to believe that its 
action would have stopped just at right angles to the axis of the 
wheel. Hence it is evident that Mr. Knight’s conclusion does 
not legitimately follow from the premises which his experiments 
present. 
We do not, however, deny that gravitation, ora power coun- 
teracting gravitation, may affect the growth of plants, and. 
influence the direction of the root or stem; or that the effect 
produced by a foreign force will be in proportion to the amount 
of the force impressed; but we contend that the vegetating 
plant possesses energies capable of counteracting the influence 
of gravitation when necessary ; and that gravitation is not the 
sole, nor even the principal agent employed by nature to give 
direction to vegetables. It is indeed a grand trial of our faith 
to have to believe that the roots of plants grow downwards and 
the stems upwards merely by the agency of gravitation. But if 
it were even granted, still the phenomenon would remain an 
incomprehensible paradox till duly explained, notwithstanding 
the result of the two experiments ; and accordingly Mr. Knight 
endeavours to poimt out the means by which gravitation may pro- 
duce the diametrically opposite effects which his hypothesis 
ascribes to it. 
He begins by saying, that “the radicle of a germinating seed 
(as many naturalists have observed) is mereased in length only 
by new parts successively added to the apex, or point, and not 
at all by any general extension of parts already formed ; so that 
the matter added being fluid, or changing from a fluid to a solid 
state, may be supposed to be sufficiently susceptible to the 
