440
[UnitJIP
every trace of the image from every part of the plate,except that which is covered with the blackened zinc,and also from the thickness of the glass the action willhe refracted under the edges of the zinc disc, and willsoften into the dark parts. Third. Mercurialize theplate as usual; the image will be found with a halo oflight around it, gradually softening into the background.By grinding the glass on which the disc is fixed, and byaltering the size and shape of the disc, a variety ofeffects may be produced.”
The appearance of these pictures is extremely singular.The fact that the exposure of plates already impressedwith an image in the camera obscura to daylight entirelyremoved the original impression, is one of the practicaldiscoveries made by every daguerreotypist who has acci-dentally lifted the shutter of the plate-holder afterremoving it from the camera. But such an applicationof this fact could scarcely have been anticipated.—R. E.]
Specimens of photography, on glass.
[The art of photography on glass is more recent thaneither the daguerreotype or talbotype processes. Butthe principles upon which it is successfully practised areessentially similar to those involved in the latter art.In consequence of the inequality of the texture of photo-graphic paper, it became desirable to obtain some morehomogeneous medium for the reception of the negativetalbotype picture. Glass and porcelain have been employedwith great success for this purpose. In order to renderthe surface sufficiently retentive of the sensitive coating ofsilver, the plates of glass are covered in the first instancewith a thin layer of the albumen of an egg, containing afew drops of a solution of iodide of potassium. The sensi-tive washes are then applied, and the plate is exposed to thelenticular image in the camera. The picture is developedin the usual manner. The “prints” from glass platesare of the most exquisitely beautiful character.—R. E.]
291a Ladd, W., 29 Penton Place, Walworth —Manufacturer.
Box of apparatus for showing experiments in pneu-matics, consisting of an air-pump and 14 other instru-ments.
[The air-pump was invented by Otto Guericke, a citizen of Magdeburg, in Prussian Saxony , about the year 1654.He illustrated the pressure of the atmosphere by thebeautiful experiment of exhausting a hollow sphere, com-posed of two pieces accurately fitting at their edges,which before the experiment were slightly rubbed withfat. On pumping out the air, the external atmospherepressed the hemispheres together with such force that, tothe great astonishment of the spectators, a number ofhorses were unable to pull them asunder. In the handsof Boyle and Mariotte it served shortly afterwards for thediscovery of the principal mechanical properties of theatmosphere.—W. D. L. R.]
Compound microscope, with chain and spindle, in lieuof rack and pinion now in use. Registered.
292 Beard, Richard, 85 King William Street, City —Producer and Patentee.
Photographic pictures by a new patent process, wherebydaguerreotypes are “ enamelled.”
[The enamelling referred to would appear to consist inremoving the glare of the polished plate by .a transparentcovering, resembling a varnish. The present method offixing a daguerreotype picture is by gilding, with a solutionof the hypo-sulphite or chloride of gold.—R. E.]
294 Kilborn, William Edward, 234 Regent Street —Producer.
Photographic miniatures.
295 Paine, William, 5 Trinity Row, Islington —Producer.
Photographic pictures, to exhibit the progress of theart.
296 Claudet, Antoine Francois Jean, 18 KingWilliam Street, Charing Cross —Inventor.
Multiplying camera-obscura, to represent on the sa® esurface a number of different pictures, or the same mvarious aspects, the portraits of several persons, &c. Thenovelty consists in moving the prepared plate by means otracks and pinions in a vertical and in a horizontal direc-tion, thus making several parts of the surface pass alter-nately before an opening placed at the focus of the lens-A sculptor being supplied with seven different aspects othe features of the same person, is enabled, without seeingthat person, to make a perfect bust or model.
Photographometer, to measure the intensity of thedirect photogenic rays, and to compare the sensitivenessof various photogenic preparations.
[It is of the utmost importance in practice to know, atall times, the amount of chemical agency ( actinism) winmay be associated with the light of the sun, as they t> ealno direct relation to each other; the light may be intenseand the chemical power very deficient, or the contra' J •hence the value to the daguerreotypist of an instrunieof this kind.—R. H.]
Dynactinometer, to measure the intensity of thefleeted photogenic radiation, and to compare the p°' fof lenses or object-glasses.
of
[Lenses vary very considerably in their powerstransmitting radiations; the difference arising from tmolecular condition of the glass itself, which varies, analso from very slight deviations from the true curveiwhich in the delicate operation of grinding it is exce
ingly difficult to avoid.—R. H.]
Focimeter. It is impossible to obtain well-defl? e jjphotographic pictures without previously ascertain 1 . 1 '^the exact position of the photogenic focus, which is easi Jdone by taking the image of the focimeter on a P 110graphic surface, and comparing the segments of ^apparatus with the image, then on the ground glass aon the photographic surface.
[Mr. Towson first observed that the focus ofchemical rays was not identical with the luminous focus^that the best photographic picture was always produceat a short distance nearer the lens, than the point at w 1the most perfect visible image is produced: M. Cla"has shown that this applies equally to achromaticnon-acln-omatic lenses; and this instrument is f 01purpose of determining the chemical focus with fa cl '—R. II.]
Screens, to modify the action of light on theparts of the figure in taking portraits, and thus o a
artistic effects. , e j ( y
Patent photographic camera-obscura. The J 1 ® 1 t j, econsists in its being possible to adapt to it wit 1 -greatest facility any system of object-glasses, to c j t0them at will according to the power wanted, and ause plates of any size; each having a separate ® oV s jjneframe, in which the ground glass and plate tit tlie r
groove. Without the least alteration it will serve f 01 . ts>
plates or paper, and answer either for views or po> 1
[The photographic camera is a modified form , 0 ^. j ecamera obscura, invented by Baptista Porta, the P 1111 o0 jyin both cases being the same, the arrangementsbeing modified to allow of the easy introduction 0 j,daguerreotype plate or photographic paper. The p 1 .