CHEMICAL AND PHARMACEUTIC MANIPULATIONS. 1 1 1 
A very curious and interesting chapter is devoted to the 
application of the polarisation of light to the discovery of 
the strength of saccharine liquids. There is not a more 
beautiful example of the value of the most recondite and 
refined discoveries in science to the practical working man, 
than is furnished by this application. 
The following chapter possesses interest for the general 
student and we give it entire. 
Construction of Formulas. 
All compounds are either mechanical mixtures follow- 
ing no precise law, or consist of simpler bodies united in 
definite proportions agreeably to the laws of chemical at- 
traction. The latter may be represented by formulas. 
There are many advantages attending the employment 
of formulas, and nothing has tended to advance the science of 
chemistry further and more rapidly than their use. They 
convey to the eye, like pictures, a far clearer view of the 
nature of a compound than the most laboured description 
could effect. While they are established by analysis, their 
reaction tends to confirm or disprove its results. As they 
are pictorial representations, the memory may retain the 
composition of thousands of compounds, and yet not be 
overburthened. Isomorphous bases may be thrown to- 
gether under a short and general expression, and thus sub- 
stances, often differing widely in external properties, are 
brought into natural groups, a result to which the analysis 
of a body would never lead without the formula. 
When a definite compound has been separated by analy- 
sis into its constituent parts, their relative proportion is gen- 
erally expressed in per centages, but such a mode of expres- 
sion does not convey a clear idea of the chemical nature of 
the body, as compared with other compounds, containing the 
same or allied constituents. The per centage composition 
is usually given as simply expressing the results of analysis. 
To ascertain the nature of the union among the constituents, 
