158 Dr. Brewster on the laws which regulate the 
more briefly than a new subject required, to give an account 
of the experiments and reasonings by which I have established 
the laws of the polarisation of light by reflexion from trans- 
parent bodies. These experiments have been extended to 
other branches of this subject, and in subsequent Memoirs 
I shall take the liberty of soliciting your attention to the laws 
which regulate the polarisation of light by transmission through 
uncrystallized plates ; — by reflexion from metallic and oxidated 
surfaces ; and by the separation of light into two pencils by the 
action of regularly crystallized bodies. In the investigation of 
the properties of metallic and oxidated surfaces, my experi- 
ments have been attended with the most successful results. 
I have discovered that the beautiful complementary colours pro- 
duced by the action of crystalline bodies upon polarised light, 
are exhibited under singular circumstances by reflexions from 
silver and gold, and to a certain degree from other metals ; — 
and that some metallic bodies have the power of polarising 
a beam of light in the plane of incidence by six or seven suc- 
cessive reflexions, while other metals are not able to polarise 
it even after twenty or thirty successive reflexions. 
Inth ese enquiries I have made use of no hypothetical as- 
sumptions. In imitation of Malus, the language of theory 
has been occasionally employed, but the terms thus introduced 
are merely expressive of experimental results, and enable 
us to avoid frequent and perplexing circumlocutions. The 
science of physical optics is not yet in such a state as to autho- 
rise the construction of a new nomenclature. When disco- 
very shall have accumulated a greater number of facts, and 
connected them together by general laws, we may then safely 
begin to impose better names, and to speculate respecting the 
