Miscellaneous Intelligence. 285 
the top and the bottom of the barrel at each stroke, by which the rare- 
faction of the air is doubled. He has obtained, with this pump, a 
vacuum of >; of an inch of mercury. 
” Photography on Glass; by T. A. Matone, (Atheneum, No. 
1179, p. 589.)—In repeating the experiment of M. Niepce de Saint- 
Victor on photography on albumen (published in the Technologiste for 
1848,) 1 was led to devise a plan of my own for making * glass nega- 
tives.” I proceeded as follows :—To the white of an egg its own bulk 
a strainer made of letter-paper so twisted as to form a cone, having a 
small aperture at its apex; pinned near the base to hold the paper to A 
its shape. The clear diluted albumen soon passed through intoawide- ©  * 
remove dust and fibres, cotton wool was used. Unless this latter and 
every other precaution is taken to prevent dust, the picture will be full 
of spots produced by a greater absorption of iodine (in a subsequent 
Process) in those than in the surrounding parts. 
Now pour the albumen on the glass, inclining the plate from side to 
side until it is covered ; allow the excess a of the corners, 
keeping the plate nearly vertical. As soon as the albumen ceases 
drop rapidly, breathe on, or warm the lower half of the plate; the 
double-ring gas-burner of some eighty jets. A common fire answers ae 
as well, save now and then it imparts a little dust. ed: 
en ; hoe a 
transparent that thé brilliancy of the glass is unimpaired. It is almost » a * 
necessary to mark it to know which side has'been coated. Se ’ +3 
rhe next operation is to iodize the plate. Dilute pure iodine with 90°, 
dry white-sand in a mortar, using about equal parts of each. Putt Te ay 
- Mixture into a square g h, and’ place the albumin 
a. late; as soon as the latter has. become yellow in color, resemb : 
beautiful stained glass, remove it into a room lighted only by a candle, g 
A or through any yellow translucent substance—yellow calico; for in- Ao 
plunge it vertically and rapidly into a deep nar 
SIX y ounces of distilled water. Allow it to remain until” . 24 
ent. yellow tint disappears, to b succeeded by a milky-) 
if jodid-of silver. Washing with distilled BF com- + @? 
We te 
res 
vy 
