Opacity of the Yellow Soda-Flame to Light of its own Colour. 55 
52. In conclusion, as every one of these theories is so de- 
pendent on every other, that it was necessary to give first a 
general outline of them all, it is hoped that allowance will be 
made for the imperfection, or even maceuracy, unavoidable in so 
brief an exposition of each. And lest, from imperfect expres- 
sion, the general principles themselves may be misunderstood, 
at may be added that the authors confidence in them arises 
only from their long-tested seeming accordance, not only with 
experimental gener aliza ations, but with scientific metaphysics. For 
every physical theory must be implicitly, or explicitly founded 
on metaphysical views as to the nature of Knowledge, as to the 
mode in which Matter and Force are to be eorieeived, and as to 
the meaning of Law. And the metaphysical bases of this phy- 
sical theory have been chiefly found in the Philosophy of Bacon, 
and of the Scottish School. 
The necessary limitation of human knowledge, the central 
doctrine of Sir Wiliam Hamilton’s system, and, indeed, the 
great result of the modern Critical School founded by Kant, 1s 
the citadel of those who would clear the Natural Sciences of 
absolute, and essentially distinct, force or forces acting on, 
associated with, or emanating from, matter. The fundamental 
conception of this theory—that of a force as a condition—is but 
a development of the doctrine of “ Forms,” “ the imvestigation of 
which is the principal object of the Baconian method of induc- 
tion*.” The conception of matter is in accordance with that of 
- substances, as ‘‘ corpora individua edentia actus puros individuos 
ex lege, ;” and that of a Law, as not an imposed rule to be 
discovered, but a relation to be expressed, seems to agree no less 
with the principles of Bacon, with whom “ the statement of the 
distinguishing character of the motion or arrangement, or of 
whatever else may be the form of a given phenomenon, takes the 
shape of a Law{,” than with the principles of Mill§. 
6 Stone Buildings, Lincoln’s Inn, 
10th Dee. 1860. 
VI. On the Opacity of the Yellow Soda-Flame to Light of its 
own Coiour. By Witt1amM Crooxes||. 
N thei remarkable investigations on the colours which certain 
substances impart to the flames in which they are heated, 
Professors Kirchhoff and Bunsen describe certain experiments by 
* Bacon’s Works, by Ellis and Spedding, i. p. 31. 
+ Ibid. t Ibid. p. 29. 
§ System of Logic, Ratiocinative and Inductive. 
|| Communicated by the Author. 
4 Chemical Analysis by Spectrum Observations. By Professors 
Kirchhoff and Bunsen. Phil. Mag. S. 4. vol. xx. p. 89. August, 1860. +5 _: 
