Mr. Knight’s Experiments on 
withdrawn ; but, as the influence of the sun increased, the clefts 
again gradually opened, as in the preceding day, and the pins 
always dropped out. I could never discover that any weight 
was gained by the wood during the night ; but I was not pro- 
vided with a balance of proper sensibility to ascertain this point. 
This experiment was frequently repeated, and always with pre- 
cisely the same result. After long exposure to the air and 
light, the wood loses this property. 
If the motion I have supposed the silver grain to possess, in 
the living tree, be more than you think can properly be admitted 
to belong to vegetable life, I will request your attention to the 
power of moving in the vine-leaf, on which I have made many 
experiments. It is well known that this organ always places 
itself so that the light falls on its upper surface; and that, if 
moved from that position, it will immediately endeavour to re- 
gain it ; but, the extent of the efforts it will make, I have not any 
where seen noticed. I have very frequently placed the leaf of 
a vine in such a position, that the sun has shone strongly on 
its under surface ; and I have afterwards put obstacles in its way, 
on whichever side it attempted to escape. In this position, the 
leaf lias tried almost every method possible to turn its proper 
surface to the light; and I have several times seen one which, 
having tried during several days to approach the light in one di- 
rection, and having nearly covered its under surface, by bending 
its angular points almost to touch each other, has unfolded itself 
again, and receded farther from the glass, to approach the light 
in an opposite direction. As the whole effect here produced ap- 
pears to arise merely from the light falling on the under surface 
of the leaf, I cannot conceive how the contortions of its stalk, 
in every direction, can be accounted for, without admitting, not 
