SCIENTIFIC SUMMARY. 
325 
duces a creamy-looking emulsion^ in wliicli is dissolved four grains of 
cUoride of sodium, or a like equivalent of any other chloride that may he 
preferred. This solution, after being filtered, is applied to the paper hy 
means of a large flat camel’s hair brush, and when dry it is ready for being 
sensitised hy nitrate of silver in the usual way. 
New Flioto-enamel Process. — M. De Luey-Fossarieu, a Parisian artist, has 
j ust published a new method of producing vitrified, or enamel photographs. 
A plate of glass is coated with a sensitive solution composed of borax, white 
sugar, gum arabic, honey and bichromate of ammonia, dissolved in water. 
When dry, the plate is exposed to light, under a soft transparent position ; 
the development being effected by brushing on suitable pigments in very 
fine powder. This adheres to the surface inversely in proportion to the 
action of the light. The film, being transferred to the enamelled tablet, is 
vitrified in a suitable mufile. 
PHYSICS. 
Electric Phosphorescence in Parejied Gases. — In a recent communication to 
the French Academy (May 10), M. Le Roux states that these phenomena 
are not alone produced by the passage of the electric spark through gases, 
but can be caused by a process of induction. When, he says, a cog- 
wheel, highly electrified, is set in rapid motion close to a tube containing a 
rarefied gas, phosphorescent phenomena exhibit themselves. 
The Phosphorescence seen in Rarijied Gases after the Passage of the Electric 
Spark. — This subject, which is one of great interest, has been inquired into 
by M. Edouard Sarasin. Instead of a tube he uses a bell-glass for the 
vacuum. After describing the general arrangements, the author observes : — 
The gases experimented on in this apparatus were, first, oxygen and its 
compounds, and then other gases containing no oxygen. Oxygen, the 
author states, always gave a persistent luminosity after the interruption of 
the current. In order to see it, he says, it is necessary to close one’s eyes 
while the current is passing ; then, on opening the eyes when the current 
has ceased, one sees a sort of pale light along the track of the spark,” or 
rather that the spark had previously traversed. At low pressures, that is 
to say at 3 mm. and lower, this light fills the bell-glass. It is at a pressui’e 
of 2 mm. that the maximum of intensity and duration is produced. No 
other simple gas gives the same results. Hydrogen, nitrogen, chlorine, and 
iodine vapours give not the least trace of phosphorescence. The compound 
gases which contain no oxygen likewise give no luminosity of this kind. 
Thus ammonia, coal-gas, and hydrochloric acid gas, give none. And the 
same may, to a great extent, be said of atmospheric air, notwithstanding the 
oxygen that it contains. On the other hand, the compounds of oxygen all 
possess this property, more or less, and some of them in a very high degree. 
The substance which produces the most intense effect is sulphuric acid. In 
experimenting on the vapours of sulphuric acid, the author simply places 
under the bell-glass a large capsule filled with the concentrated Nordhausen 
acid. Then, when the air is exhausted, the vapour of the acid rises and 
