It is a small speck in the middle of the sea, lying so near the level of the water as to be unobservable at any considerable distance.
"The Campaigns of the British Army at Washington and New Orleans 1814-1815"
G. R. Gleig
In zoology, for example, there is an immense number of uniformities ascertained, some of coexistence, others of succession, to many of which, notwithstanding considerable variations of the attendant circumstances, we know not any exception: but the antecedents, for the most part, are such as we cannot artificially produce; or if we can, it is only by setting in motion the exact process by which nature produces them; and this being to us a mysterious process, of which the main circumstances are not only unknown but unobservable, the name of experimentation would here be completely misapplied.
"A System Of Logic, Ratiocinative And Inductive (Vol. 1 of 2)"
John Stuart Mill
At no age in boyhood, nor yet in manhood, could a single performer, or a host of men, have accomplished by unobservable processes and forces all that is distinctly stated to have been performed in and around the house of William Morse.
"Witchcraft of New England Explained by Modern Spiritualism"
Allen Putnam