Popular Science Lectures. 163 
ment in such common use among the planters of the 
colony, that the theory of polarization is probably as 
well-known to every one connected with sugar, as its 
practical application. It is an abstruse subject — polarized 
light — requiring diagrams for its elucidation, and as I am 
only mentioning — not describing these triumphs of 
science it may be sufficient to remind you that a beam of 
ordinary light transmitted through certain substances 
or reflected from pieces of common glass, undergoes a 
change and becomes polarized. A ray of this polarized 
light passed through, for instance, a column of syrup and 
viewed through an arrangement of spar indicates by 
certain changes of colour the presence, and the degree of 
cane or grape sugar present in such syrup. 
The Polariscope in its simplest form is easily made and 
though a more complete instrument is required for 
purposes of exact analysis, yet with such an one as an 
amateur can make interesting results may be obtained. 
I have omitted, but have not forgotten to mention 
electricity as giving us what may be termed the light of 
the future, " electric light." It is to be regretted that 
its more general use has been so long retarded by diffi- 
culties which will no doubt be overcome in time, when 
we may see it introduced in the streets if not the houses 
of this city. The purposes for which electric light can 
be employed are many, one of the most curious being 
the lighting on his submarine road the pearl fisher of 
the East. 
While on the subject of light I may refer as another 
instance of the benefits derived from science, to the dis- 
covery of petroleum and the means of refining it so that 
in place of the dim rays of the old, cheap and nasty 
X 2 
