378 
VARIETIES. 
and thus brought into the market. M'Culloch states that sago is used in 
thickening it. This, however, at least in Singapore, is not the case; 
but, instead of sago, a piece of vfood is dipped into the vessel, by 
which the desired effect is produced. It must, indeed, be an extraordi- 
nary substance, the mere dipping of which into the fluid can cause it to 
become a thickened mass. I was very eager to obtain a piece of this 
wood ; unluckily, the Chinaman whose laboratory I visited, could not be 
persuaded to part with his, and a friend of mine, who was exerting him- 
self to procure a sample, had not succeeded at the time of the Herald's 
departure ; he promised, however, to send it to England, accompanied by 
the Malayan name, and specimens of the tree. — Ibid., from Hooker's 
Journal of Botany. 
On the Production of Photographs on Glass. By J. Pucher. — According 
to this process, a thin film of iodide of sulphur is formed upon plate glass, 
which must be perfectly clean, with a very thin coating of sulphur, and 
then impregnating this for a few seconds with the vapor of iodine. The 
glass plate is then placed in the camera, where at the same time the vapor 
of some quicksilver in an iron cup in the bottom of the camera acts upon 
the iodide of sulphur with which it is coated, and it receives the photo- 
graphic image within a minute. The glass plate, when taken out of the 
camera, only exhibits a trace of the picture, but this immediately comes out 
on exposure to the action of the vapor of bromine. If the picture be now 
held over alcohol, and some of the same liquid be poured upon it, it will 
be fixed. Not more than from five to eight minutes are required for the 
whole operation. 
The glass plates must be breathed upon and well rubbed with a soft linen 
rag several times before use. They are coated with sulphur by burning 
sulphur sticks, made on purpose, in a proper tube, and holding the plates 
over it at a distance of about 3 inches. These sulphur sticks are prepared 
by dipping pieces of rush-pith into a melted mixture of sulphur and mastic, 
with which they become incrusted. For use, these sulphur sticks, which 
are about the size of a lucifer match, are stuck on a brass needle, introduced 
into the middle of a glass tube and kindled, so that the vapor of the sulphur 
may come in contact with the glass plate held over it. 
These glass plates are so sensitive, that the coating of iodide of sulphur 
becomes instantly changed on exposure to direct sunlight, and give a 
Moser's image within five minutes when laid in a book. The figures thus 
obtained are most easily read by candle-light. In daylight, the blue letters 
can be recognized on the yellow ground only by looking through the plate 
towards the middle of the window, or towards a sheet of paper fastened in 
that place, the sulphur not having been removed either by vapor of bromine 
or by alcohol. 
If a glass plate covered with a solution of gum and exposed to the vapor 
of iodized sulphur, be placed in the camera, a positive picture, with all its 
