5»4 
BEES AND BEE-KEEPING. 
is stopped, and every wire that can pass the first 
grating is stopped by the second; and similarly re- 
ferring this to light, two prisms placed with their 
planes crossed — e.g.^ one perpendicular, and the other 
horizontal, will stop all light. 
Let us imagine a tube Fig. 125) containing 
levulose in solution, held in by flat glass plates, to be 
put between the two prisms ; the plane of polarisation 
of the light will then be revolved, during its passage 
through the levulose, towards the left, as at ef. If 
there be sufficient levulose, and the tube (^) long 
enough, perpendicular waves may be made horizontal. 
The amount of rotation is ascertainable by noting 
the position the second prism must take to exactly 
counteract the effect of the rotation caused by the 
levulose. Dextrose gives the opposite result ; but 
since equal quantities of the same description of sugar 
always produce the same number of degrees of rotation, 
these quantities can be determined by an examination 
by polarised light. 
The main adulterant of honey is corn syrup,* pro- 
duced in America in enormous quantities by the action 
of acids at high temperatures upon the starch of 
maize. The starch is not wholly converted ; some of 
it remains in the form of dextrine, a kind of gum, 
but the bulk is transformed into dextrose. Honey 
so adulterated would rotate the plane of polarisation 
to the right, whereas the opposite tendencies of the 
equal quantities of dextrose and levulose in pure honey 
would leave the plane of polarisation little affected, 
although, as levulose has more rotatory power than 
* “Adulteration of Honey,” Otto Hehner, page 12 . 
