286 Miscellaneous Intelligence. 
is only by considerable management of light that I can begin to see the 
lines alluded to; another similar instrument by the same maker, would 
not show them at all. Only one out of three of Oberhauser’s which I 
have examined, showed the lines, and then much trouble was experien- 
ced in getting the right illumination. The performance of the Ross 
well as the longitudinal ones were easily seen, and without requiring 
much maneuvering of the mirror. It is with these that I compare the 
the most awkward illumination.” This he has done, and not only can 
the lines be seen in almost any position, but when properly illuminated 
they are shown so distinctly, that I have found no difficulty in copying 
them by means of a camera lucida, and I have thus ascertained that the 
distance between the cross lines referred to, is not more than one forty 
thousandth of an English inch! Such is the performance of Spencer's 
lenses in my hands, but the artist says they will do still more, and that 
by means of those I now own, he has resolved the lines on a sigmoid 
Navicula which I found in the Croton water of New York—an object 
to which, as Spencer says, “all other test objects are mere child’s play.” 
This animalcule has a shell not more than half the size of that of the 
individual N. hippocampus above referred to. It is possibly the young 
the same species, but as it appears to be uniformly much smaller, 
and its markings are far more minute, | shall consider it at present as 
a new species, and dedicate it, by the name of N. Spencerii, to the per- 
son who first resolved its lines, by instruments of his own making. This 
object, which from analogy 1 judged to have lines resembling those on 
the N. hippocam us, was sent by me to a friend who possesses one 0 
the best foreign instruments. After giving it a long and careful trial, the 
gentleman to whom it was sent informed me that he had tried in vain 
to see the lines in question, and he adds that if Spencer’s lenses wi 
show them, they must surpass the best European instruments. Now 
although I cannot positively state that I have seen the lines with Spen- 
cer’s lenses, the artist himself has seen them with the same objective ; 
and that I have not yet succeeded, may possibly be due to some defect 
in the eye-piece (one of Chevalier’s) with which ] have to combine it. 
That the lines exist, I should have no doubt from the peculiar appear- 
ances I have myself seen, even if we had not the positive testimony of 
Mr. Spencer that he has seen them clearly and unmistakeably. Lenses 
which will show these lines, (which cannot be more than one eighty 
thousandth of an inch apart,) may safely challenge competition with 
foreign microscopes. 
West Point, N. Y., Feb. 4th, 1848. 
