glass cell in which algae or animalculae are placed for observation.
A peculiar style of engraving on metal said to have been invented by St. Non, a French artist, about 1662.
Otherwise stated to have been invented by Le Prince, Metz, 1723.
The process, briefly described, is as follows: A surface of resin is spread upon a polished plate in such a manner as to leave innumerable little interstices between the resinous particles.
This surface covering is called a ground, and ma per head of fifty cubic feet, or three hundred and twelve gallons, per diem, — a consumption quite unequalled in modern times, except in the city of New York, where it is said to have formerly amounted nearly to this quantity.
The aqueducts of Metz, Nismes, and Segovia are also striking examples of the attention paid by the Romans to the subject of supplying water to their towns and cities.
It does not appear that the ancients were by any means ignorant of the applicability of pipes for c
effervescence, penetrating the unaltered gelatine and preventing its disturbance by the evolution of gas.
A process of transforming photographic plates into colored enamels.
Two methods are employed.
In the first, introduced by De Camarsac of Paris, colored vitrifiable powders are applied with the pencil to the different parts of the proof on glass, and the whole is raised to the necessary heat in a muffle.
In the second, that of Tessie du Motay and Marechal of Metz, the photographic proof, taken in the ordinary way, but made as forcible as possible, is immersed in solutions of other metals by which the silver is displaced.
If this be done successively in several baths, with exposure of different parts of the device in each, the subsequent process of enameling will furnish corresponding varieties of tint.
（Photography.) A chamber in which a sensitized surface, usually a glass with a film of sensitized collodion, is exp
and has been reproduced in modern times.
See the Spiritalia Heronis.
C shows the ordinary siphon; it is filled with liquid, the ends stopped, and the shorter leg immersed in the vessel from which the liquid is to be drawn; the longer leg being placed in or over the receiving vessel.
On opening the ends a continuous flow is maintained until the level of the liquid in the upper vessel reaches that of the orifice in the shorter leg of the siphon
B shows a large siphon used at Metz, in repairing a dike on the Moselle.
To put it in operation, the ends were stopped with plugs and the siphon filled with water through a funnel a, the air being permitted to escape through the cock b. When full of water, this was closed with a cover c, provided with a tubular glass top, which permitted a view of an indicator-needle on a float, which showed at what hight the water stood as its level became gradually lowered in consequence of the air contained in the water accumulating at the