360 
SUMMARY OF CURRENT RESEARCHES RELATING TO 
concave mirror is enclosed in tlie case and is moved by means of the 
small brass milled head outside the case. This Microscope is supposed 
to have been made about 30 years ago by Messrs. Nachet and Sons of 
Paris for Dr. Mouat, for use in India. 
Fio. 53. 
Fig. 52 shows the instrument arranged for use. Fig. 53 shows the 
instrument packed for carrying. 
(2) Eye-pieces and Objectives- 
The new Zeiss Patent Binoculars.* — Mr. E. M. Nelson gives an 
account of these new instruments. There are two kinds : one cor- 
responding to the binocular field-glass (fig. 54) and the other to the 
binocular telescope (fig. 55). They are both astronomical telescopes 
consisting of an object-glass and a Huyghenian eye-piece, and the 
erection of the image is effected by two prisms. In the case of the 
simple telescope there is probably a greater loss of light by this prism 
Fio. 54. 
arrangement than with the ordinary erecting lenses, but in the case 
of the field-glasses several important points are gained by discarding 
the Galilean principle. Thus the large field and even definition of the 
Huyghenian eye-piece are secured. The most striking feature of the new 
instrument is that, to secure portability and increase the stereoscopic 
projection, the axis of the object-glass is not in the axis of the eye-piece. 
The author’s notion of the arrangement of the object-glass, prisms and 
eye-piece, is seen in fig. 56; the rays are bent back twice, so that the 
instrument is reduced to about 1/3 in length. 
* English Mechanic, lx. 0894) pp. 344-5. 
