1897 THE MICROSCOPE. 159 
These requisites can now all be readily obtained from 
any good dealer in projection apparatus. Many plans 
for ‘‘shooting’ the fibres have been proposed; but I 
have never found anything more simple or satisfactory 
than the original bow-and-arrow method of Prof. Boys. 
For silvering them I prefer Brashear’s method. To 
get a good coat it is, however, necessary to clean the 
fibre very carefully. For this purpose I have found it 
best to use in succession very hot solutions of strong 
nitric acid and strong potash, and then wash in several 
changes of clean distilled water before immersing in 
the silver solution. In order to handle the fibres during 
these operations, I have found it convenient to mount them 
on a small rectangular glass frame with a bent handle, 
similar to that shown in the figure. The ends of the 
fibres are secured to the upper and lower bars of the 
frame by fused (not dissolved) shellac, which resists well 
the action of the hot acid and alkah. In lifting the frame 
in and out of the solutions, care should be taken to move 
it vertically up and down, otherwise the fine fibres will 
be broken by the surface tension of the liquid surface. 
On such a frame a dozen fibres may be silvered at once; 
and then set aside for use as desired. 
Another great advantage which such silvered fibres 
would be likely to possess when used in bright wire mic- 
rometers—i. e., that of perfect and uniform illumination 
was pointed out by Prof. Burnham. To get the best re- 
sults in such a case a cyJindrical mirror should be placed 
behind the wire (on the side away from the source of il- 
lumination) with its axis parallel to the length of the 
wire. 
New Factory.—As soon as our new building is com- 
pleted we will be pleased to send you a cut of it together 
with a description.—Gundlach Optical Co., Rochester, N. 
Y., H. H. Turner, Manager. 
