Wgdom.]
AND SURGICAL INSTRUMENTS.
North, North Central, and South Central Galleries.
441
the' S .°^ teu P 0 P u lai'ly studied by simply making a hole intrindow shutter of a dark room and examining the8®s of external objects on a sheet of paper at a certain‘Stance from it.—R. H.]
^ ' 50xes > for containing the prepared plates, andv,7 In g them to and from the camera-obscura.c °nt^ S t ^ lames ’ to hold tw0 plates, face to face, without
o^cury box. The novelty is that a number of platestic sizes may be mercurialized at once, in a ver-
tem Position, and that the heat is applied by the uniforma perature of boiling water.
pl^rPParatus for cleaning and finishing a daguerreotypethe 6 ’ without burning the oil which has been used for0 f Polishing, and without employing cotton wool, spiritJt'tne, or any powder.
, Jr foiuide of iodine. Iodine and bromine combined in^portions found to afford means of giving the plate the° test state of sensitiveness.
th^ n P re P al ’! n S a daguerreotype plate, it is essential that. e agent employed to act chemically on the polishedaj ^ er surface should be in such a condition, that the>uty m a y be easily upset by solar agency. This isP e euliav]y the case with compounds of bromine, iodine,Q chlorine. The balance of action is very easily dis-e( l» and hence the extreme sensibility of plates pre-a ‘cd with these compounds.—R. H.]
Se ^* a guerreotype pictures, plain and coloured. Repre-eff ta * Ion of objects of art, scientific experiments on the4 °f the various rays, illustrations of the non-coinci-®at° e t ' le v r sua l and photogenic foci, portraits fromobi Ure ’ ta ^ en l>y means of a prism placed before theJ c t-glass, in order to obtain a non-inverted picture.
infl^ e e ff ec t s shown in these experiments illustrate theHu ll< “ lces exerted by various media, natural and artificial,‘he solar rays. In some examples, the luminous
an? - are s ^ own to act as protecting the plates from change,/ 111 others the energetic power of the chemical rays
r ° Wls >«) is separated to a great extent from the luminoust Qfyht). The general result is to prove that theal 7 at ‘ ons "which give rise to photographic phenomena,hough associated with light and heat in the sunbeams,, e not identical with it in their action on material
0( lies.—u,_ h.]
4ucr 0tosra Phi° table; showing that photographic pro-bienn may he employed in various ways, as the orna-al part of drawing-room furniture.sp ec ?S uei 'reotype plates, perfectly plane and free fromis > forming true mirrors.
hy 1 ^ erre °tyP e P' ates are °P C0 PP er > plated with silver;Uea ac ‘ n ® two pieces of these metals in contact with veryf 0 i. surfaces, and thus passing them through steela ct j o rs ’ Ihey are pressed so closely together that the full® °P eohesive force is exerted between their particles,e y a dhere with great firmness. The silver is sub-f 0r polished, and by nice manipulation prepared
Ph 6 USe da S' ierreot yP e art l s t.—R- H.]
tfie a h>genic paradox, showing that what is light for“"otai ' ls •Urkness for the photogenic action; a framec 0 y 011 one half, the portrait of the Queen,
Povtm't w ‘lh yellow glass, and on the other half theP e iiig 1 PUnce Albert, covered with deep blue glass,is t} 1 ^ t r< ‘P r( ' scn te , l on a daguerreotype plate. The resulteye s th ‘ ‘e yellow glass, although showing clearly to thetog ( , r • e Picture of Her Majesty, has prevented the pho-Coit iblet ^ ct ‘°. n \ and that the deep blue glass, although*°8enic ^ hiding the portrait of Prince Albert, the pho-glass h ray ?, redec ted by his picture through the bineif th e en Ve . ■ d tdle same a ®tion on the daguerreotype as°r Wi* ® rav ‘ n g Pad been covered with transparent glass,n ° glass at all. This experiment proves why
when light appears yellow on account of vapours existingin the atmosphere, the photogenic action is always sofeeble and altogether impeded.
Frame containing six specimens.
(1) Light of a candle represented on a daguerreotypeplate.
(2) Image of a statue produced by the continuedaction of light on a daguerreotype plate, without anymercury; the white forming the image is due to a fineprecipitate of the silver combined with iodine, taking-place under the action of light during the decompositionof the compound.
(3) Negative portrait produced on a plate first exposedto light, and in that state having received the image ofthe camera obscura through yellow glass; this provesthe destructive action of the yellow rays in the photo-graphic operation, and that the yellow rays are not onlyantagonistic to the photogenic rays, but that they destroythe effect produced by the last.
(4) Image of the sun produced during a clear atmo-sphere.
(5) Image of the sun produced when it appears redthrough a fog.
(6) Image of the moon produced during a clear night.
Frame containing four specimens—
(1) Image of the solar spectrum on iodide of silver.
(2) Image of the solar spectrum on bromo iodine ofsilver.
(3) Experiment of the focimeter, showing the differ-ence between the visual focus and the photogenic focusand their variation.
(4) Experiment of the dynactinometer, showing theintensity of the photogenic light at any given moment,for various spaces of time in a geometrical progression.It is curious to observe the small difference produced bya double intensity.
Image of clouds, taken instantaneously during bois-terous weather. Interesting study for artists.
Frame containing the various colours of water colour,and another the daguerreotype representation of thefirst. This experiment shows that all the tints ofblue, indigo, and violet produce white in photography,and that all the tints of green, yellow, orange, and red,produce black, or rather that they have no photogenicaction.
297 Henneman & Malone, 122 Regent Street,Westminstei —Designers.
1. Talbotype apparatus of improved design, made byJ. Newman, of 122 Regent Street.
2. Talbotype pictures produced on paper, silk, andother fabrics; and on porcelain, coated glass, stone, steel,wood, and ivory.
3. Talbotypes treated with caustic potash and a leadsalt, in order to produce an agreeable tint of colour, andto render more secure the fixation.
4. Specimens of Sir J. Herschel’s eyanotype and chry-sotype, and of Mr. Robert Hunt’s chromatype pictures.
[Talbotype is the name applied, in the first instance,by Sir David Brewster, to the calotype pictures, hisobject being to distinguish by the name of the discoverera photographic process which is little, if anything, infe-rior to the daguerreotype of the French . Paper beingcovered with a pure iodide of silver, is rendered sensitiveto luminous radiations by being washed over with a mix-ture of gallic acid and nitrate of silver; and after thepaper is taken from the camera, a dormant picture beingproduced upon it, it is developed by a second applicationof gallic acid.
Sir John Herschel’s eyanotype and chrysotype processesadmit of many modifications, the former consisting of thechange of a persalt of iron into a protosalt by the solarrays; the paper being then washed with a compound of