314 Progress of Invention, 



ing, that the union of both is indicated by a line, a circumstance 

 quite sufficient, if irremediable, to render the contrivance inadmis- 

 sible. This difficulty is, however, easily obviated by the use of a 

 suitable diaphragm placed within the camera at a proper distance 

 from the objective and the glass plate. There is thus produced a 

 kind of penumbra in one position, which is rendered perfect by 

 exposure during the next position. The impressions corresponding 

 to the successive portions of the view being in this way made to 

 blend with each other, so that no line of demarcation between them 

 can be perceived. Five or six movements of the camera and the 

 plate are found quite sufficient for a very extended view. 



Application of Air charged with Combustible Vapours. — 

 Inflammable gases are frequently rendered capable of imparting a 

 more brilliant light, during combustion, by charging them with 

 hydrocarbon vapours. Experiments are, however, being made at 

 present in Russia with atmospheric air charged with these vapours, 

 and the result is said to be the production of a combustible gas 

 capable of affording a heat sufficiently intense to melt steel. Atmo- 

 spheric air is forced through oil of turpentine, and carries along 

 with it an amount of the fluid sufficient to cause, during its com- 

 bustion, not only the evolution of an intense heat, but the emission 

 of a clear and brilliant light. It is intended, in this way, to provide 

 fuel for some small steamboats which are intended to run on the 

 Neva. Such an arrangement may be found convenient, and even 

 economical, in certain circumstances ; but if it is used, it will be 

 necessary to guard against the danger of explosion. This, how- 

 ever, may be done by very simple means. 



Miscellaneous. — Neiv Application of Photography. — Photography 

 now enables us to obtain the picture of a projectile passing out of 

 the mouth of a gun. For this purpose it is necessary to have a col- 

 dion which requires a very short exposure, and a means of rendering 

 the exposure and the ignition of the charge perfectly simultaneous. 

 The latter, which would be impossible to any degree of manual 

 dexterity, is effected by very simple and infallible means. The 

 current of galvanic electricity which by rendering a thin platina 

 wire incandescent, explodes the charge, excites an electro-magnet 

 that raises a disc from the front of the lens of the camera. 

 When the wire has melted, that is, when the ignition of the 

 charge is complete, the disc falls in front of the lens. Rein- 

 forcement of Photographic Negatives. — A negative may be imperfect 

 from insufficient exposure, in which case the details will not be 

 well brought out : or from the collodion, the silver bath, or 

 the developer being out of order, in which cases it will not be 

 sufficiently opaque. The former imperfection may be removed by 

 means of pyrogalic acid, to which has been added citric acici and a 

 few drops of aqueous solution of nitrate of silver. The latter, by 

 means of, first, an aqueous solution, containing three per cent, of chlo- 

 ride of copper, then washing with water, applying an aqueous con- 

 centrated acid solution of sesquichloride of iron ; again washing, then 

 applying an aqueous solution of iodide of potassium, which has 

 been saturated with pure iodide of silver, and finally washing. If 



