28 On the Action of the Second Stirfaces of 
flowers as things of the same sort, because the same word recals — 
them ; nor is it essential that any image should be recalled to the 
mind by the word subjects, to make it convey truths to our under- 
standing ; as if we say, ‘all the subjects of God’s creating power de= 
pend on him for continued existence :”—and the figure 2 might call ~ 
up mental pictures of stars and flowers, even though the eye cursorily. 
caught it in the date of the present year, 1832. As thus—I. readin 
a book, “ Pictures of 2 sorts of things, stars and flowers.” Here 
the uncommon use of the figure 2 might have so struck me as to re= — 
mind me, the next time I saw it, of the sentence in which it was thus 
used, and the mental-pictures of these objects thus be brought tomy — 
mind ; and if so, is it not the same process by which the word su 
jects mlabi suggest them ; and when they are suggested, does not the 
ind, in both cases, take cognizance of them as of two sorts of things,’ 
so unlike that no common name or common relation can make us 
conceive of them as of one kind. Yet by means of a name express- 
ing a common relation, we can reason and speculate about them in 
connexion, though we cannot conceive of them as of the same sort. 
If these facts are admitted, we think it must follow, that the doctrine” 
of the nominalists is no less true with regard to terms expressing ar- 
tificial classification, than is that of the pice geet with = to 
tae — natural classes. 
Arr. V.—On oe action of the second surfaces of meal plate 
wake by Davin Brewster, LL.D, F.R.S. Lond. Sze 
ae is Read before the Royal Society, February 25, 1830. 
‘Ina paper on the Polarization of Light by Reflexion, aoianea in 
the Philosophical Transactions for 1815, I showed that the Law of 
the Tangents was rigorously true for the second surfaces of transpa-_ 
rent bodies, provided that the sine of the angle of incidence was less 
than the reciprocal of the index of réfraction. ‘The action of the 
second surfaces of plates at angles.of incidence different from the 
maximum polarizing angle, was studied by M. Arago, who conduct 
ed hi in the following manner. 
ith respect to this phenomenon,” says M. Arago, a remarka-- 
ble result of experiment ney here be —z ; that is, that en every. 
possible sclination A=A’.* 
aie 
” A is the light polarized by reflexion, dnd A’ that polarized by refraction. 
