1902] MICROSCOPICAL JOURNAL. 123 
being afforded by the objective which is being employed. 
There is one infallible proof to which all theories, how- 
ever profound or ingenious they may be, or however much 
we may admire the labors of their authors, have always, 
sooner or later, to submit, and by which they must in- 
evitably stand or fall: and that is, observed fact. When 
a new and brilliant theory or any philosophical subject is 
first promulgated by some eminent scientist, it is the ten- 
dency of self-elected disciples, exponents, and admirers 
to permit themselves to be carried away by their enthu- 
siasm, and go to lengths in defending and expounding 
the new tenets that their author would be perhaps the 
first to deprecate. Forgetting the lessons of the past 
that few indeed are the theories which have withstood 
the test of time unscathed, they from the outset regard 
matters not from a strictly impartial, but from a purely 
partisan standpoint, and while eagerly calling attention 
to and exaggerating the significance of such observations 
as may appear to them at the moment to favor their 
views, they on the other hand, heatedly call in question 
and throw doubt upon those which tend to the contrary, 
often without patient inquiry or experiment, It has been 
said that even a bad theory is better than none atall, and 
this is undoubtedly true in so far as it paves the way for 
that calm philosophical discussion from which we may 
hope to eventually attain some nearer approach to the 
truth, as distinct from controversy and personal recrim- 
ination, which can only serve to retard progress. 
I amaware that many supporters of the diffraction 
theory, being not only theoretical but experienced and 
skilled practical microscopists, have now tacitly admitted 
the value of large-cone illumination, apparently realizing 
the wide gulf that such an admission has opened between 
their views and those of the author of the theory. In this 
connection it is instructive to notice that the deductions 
contained in the clear summary of the diffraction theory 
