282 New Combinations with the Camera Lucida. [Ger. 
Many circumstances occur to recommend these adaptations, with- 
out including the superior gratification of being able to copy with 
certain correctness the forms of minute or inaccessible and distant 
objects, when compared with that of retailing appearances, which 
are open to every beholder. The great dificulty which even an 
experienced artist finds, in representing with tolerable accuracy a 
telescopic or microscopic image viewed in the usual constrained and 
interrupted manner, will render this improvement highly desirable. 
The astronomer, and even the military officer engaged in recon- 
noitring, would derive important assistance from the use of the 
graphic telescope. 
The patent for the Camera Lucida remains, I believe, with the 
illustrious inventor ; and his sagacity, which has perhaps anticipated 
the hints conveyed in this paper, will immediately discover the best 
methods of applying them to experiment. Those methods which I 
take the liberty of noticing are simple, and such as I have partially 
submitted to trial. 
The obvious principles which require attention in both the adapta- 
tions recommended are, to immerge the object-face of the prisim 
into the cone of distinct rays which issue from the eye-glass of the 
other instrument, further than is permitted by the usual eye-piece ; 
and to allow a close approach of the eye to the upper surface of the 
prism. These precautions evidently tend to secure a sufficient extent 
to the field of view. ' 
The graphic microscope would perhaps be constructed in the best 
manner by attaching a single microscope to the object-face of the 
prism. ‘The appendages of pliers, &c. might be made applicable 
to the shaft or style of the camera. ‘he vertical structure, and 
other properties of the compound microscope, present obstacles 
which it would not be easy to surmount. And the solution of these 
difficulties is the less necessary on account of the facility afforded 
by the construction of the camera lucida itself, for enlarging or 
contracting the dimensions of the apparent image at pleasure. 
In the telescope the perforated cylindrical cap, which is screwed 
over the eye-glass, may be exchanged for a shorter, conical, or 
cuneiform cap, having a larger aperture. This cap might carry an 
arm, perforated to admit the axis of the prism. A still preferable 
method is, to take off the perforated cap, and attach a hollow tube 
to the side of the eye-piece. In this tube, which must of course 
be shorter than that in which the stem of the camera slides, a 
similar stem nmiust be inserted bearing the prism: in short, the 
original instrument, cut off at one third of its length, must be 
attached to the tube which contains the eye-glasses of the telescope. 
The telescope being adjusted to a proper focus, and the stem of the 
camera drawn out toa due length, and turned, to bring the prism 
opposite the axis of the telescope, the aperture of the eye-piece of 
the prism being also placed in such a manner as to exclude, if re- 
quisite, the superfluous rays; the objects toward which the instru- 
ment is directed will appear, on looking through the prism, to be 
