PHYSICAL anv LITERARY. 27 
the luftre of the drop arifes from a copi- 
ous reflexion of light from the flattened 
part of its furface contiguous to the plant: 
I obferve further, that, when the drop 
rolls along a part which has been wetted, 
it immediately lofes all its luftre; the 
green plant being then feen clearly thro’ 
it: whereas, in the other cafe, it is hardly 
to be difcerned. 
17. From thefe two obfervations laid 
together, we may certainly conclude, That 
the drop does not really touch the plant 
when it hasthe mercurial appearance, but 
hangs in the air at fome diftance from it, 
by the force of a repulfive power; for 
there could not be any copious reflexion 
of white light from its under furface, un- . 
lefs there were a real interval between it _ 
and the furface of the plant *, [See Tas. 
ji. Fig.2-] ; 
Pe 
* Newt Optics, query 29, 
Let AB, Tas, iii. Fig. 4. reprefent the extremity of , 
any repulfive body immerfed in water, for inftance a flice 
of colewort leaf, CL, and DM, the convex {urfaces of 
_ Water immediately furrounding it, and CD perpendicu- 
Jar 
