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THE PHOTOGRAPHIC NEWS. JANUARY 26, 1883.] Two condensing lenses, one to render the rays of the focus. to the amplification you intend to employ or the nature of the » Bead at the Quekett Microscopical Club. suring by its sticky nature, when damp, the immovable adhesion of the paper to the lithographic stone during the process of transferring in the press. (To be continued.) occupied by a dry gelatine plate, and the exposure accurately timed according to the nature of the object; but only experi ments can determine this. Care must be taken before making the exposure that the light through the objective be cut off till the plate is in position, when it may be allowed to fall on the plate for the requisite time, and then cut off again before removing the plate to the developing dish ; this is done, as must be evident to you all, to avoid blurring the image. I need not say that the only outside light must be a non-actinic red light, and no ray of white light must be allowed to reach the plate, or it will be “ fogged ; ” that is, when it is developed, it will be veiled by a misty deposit in the film ; therefore no actinic light is admissible till the plate is fixed. PHOTO-MICROGRAPHY. BY T. C. WHITE.* This being one of a series of demonstrations and not a lecture, it is not my desire to occupy your valuable time and attention by making more than a few preliminary remarks necessary to your fully understanding those essential details in the art of tive till he can produce a good result on every occasion, when a fresh one may be tried ; the time of exposure being greatly varied by the magnifying power employed, the lower powers admitting of a shorter exposure as more light passes through them. The principles upon which this beautiful art is founded may be read in any of the many manuals on photography, and which are published at a cheap rate ; therefore, leaving these, I will pass on to the practice. If anyone needs to learn about the various apparatus employed for photo-micrography, full particu lars will be found in Beales’ “ Howto Work with the Micro scope,” and in Cutter’s “ Microscopical Technology,” both of which works are in our library. In the first place, I claim for my plan, its great simplicity, being, as you see, nothing more than a lidless box placed on its side ; at the left end it has a square hole, but any aperture will do ; a brass plate, having an adaptor in it, slides in and out on runners for more easily changing the powers when it is desired to do so. Another long aperture is made at the top side, covered by a blackened chimney to carry off the heat from the duplex paraffin lamp inside ; another aperture at the bottom of the right side serves to admit the air to the lamp when the front I of the box is covered up by the black focussing cloth; within the box, and attached to the left side, is a carrier working on a long I and fine screw, which serves to adjust the object to the correct photo-micrography which may serve to start you fairly in this very interesting occupation for winter evenings. I would in the first place remind you that I do not stand here as an oracle on the subject, but simply come before you at the wish of the higher powers of the Club, to do what I have so often done I before, and that is, to stop a gap which might have been filled by others more efficient, but at the same time more modest. It is a very true saying “ that if the blind lead the blind, shall they not both fall into the ditch ?” Now it is far from my in tention to land you with myself in this ignominious dilemma ; I shall only show you the method I have employed for my own recreation, and if any of you like to follow my steps, you mav be able to introduce many improvements, and serve to advance lamp parallel, and the other to condense them on the object, the art, which has many fascinating charms about it for the en- 1 ■ • • ■ • • ’ 1 1— lightened worker. you could, or would you stand still to sink for ever in it, because I hundreds of others had tried to run, but had generally sunk to be seen no more ? I reckon that you would “ make tracks ” to I get out as well as you could ; and this illustration may be used I as an argument in advocating the further study of this art. It I is not because our predecessors have been, as it were, floundering I about in the practice of photo-micrography, that we are to rest I content. But I deny entirely the assumption that they did I nothing worthy of our admiration, or sufficient to encourage us in our endeavours after perfection. I grant that the art is sur rounded by many and great difficulties, and only the application | of close study, and the concourse of many minds, can tend to its advancement; but while it is neglected or limited to a few practitioners, its advance must be slow. I am glad to see by the photographic journals that many in the provinces and abroad are awakening to the interest attached to this process, and much good will result. 1 must, however, pro ceed to the subject of this evening’s demonstration. The method most generally practised, and recommended, is that the micro scope being placed in a horizontal position, its tube should be attached by a blackened tube or a cone to the front of a photot I object may indicate, or, if lantern slides are desired, on a square graphic camera, the lens of which has . , 3, inches ; these ought to have a piece of smooth writing paper find these difficulties arise. It is not e Y 8 gummed on that surface presented to the image. The image is camera, and they may not feel disposed to go to the expense of then thrown on to one of these, and, the hand placed under the procuringone, while all the members.of this Club possess[micro- focu8sin g. clot h, the carrier is to be moved by means of the scopical objectives ; but, further, i they have a camera, it is not screw adjustment till the image of the object is sharply defined an easy matter to see the fine details of a subject through the on the screen ordinary ground focussing glass. Again unless the camera and In many writings on this subject it is stated that the actinic microscope are securely fastened down to a base- oar , ere is and visual foci of microscopical objectives are not coincident. AR a endency to unsteadiness which is irritating in the ex reme , Ican say is, that with a J of an inch, which I shall employ this an ur , ermore, this usual plan does not oiler any advantages 1 evening, and with Zeiss’s D, no alteration is needed from the ver, a .wish,to introduce to your notice this evening.. n visual focus. The screen may now be removed, and its place -ne apparatus before you, and which I have found so convenient, | - - - - - - - - - •• - it is not necessary to have either a camera or a microscope, and is so simple that it can be adopted by the youngest member of the Club; but even with this, difficulties will arise which are altogether apart from the apparatus ; for instance, objects differ in their capability of transmitting the actinic rays ; they may be too opaque, or brown ; or they may be stained blue or red. All these conditions vary the time of exposure, only experience teaching the requisite time to imprint the image in the sensitive film just sufficiently without under or over-exposure; this must be left to the cultivated judgment of the operator. Great assistance will be derived by the beginner sticking to one objec- complete the arrangement as far as the box is concerned. The CL , ,i light passing from these through the objective emerges as a cone, It has been often asked by numbers of those fossilised indi- and on the principle of a magic lantern projects the image on a viduals who may be found in great abundance, ‘‘What is the screen to the left of the operator. good of making photographs of microscopical objects ? It has I The screen consists of a heavy piece of wood having a groove been tried over ana over again, and found no good; it can’t be I formed in it, and carrying another block upon which the screen done. 1 o such I would reply : If you found yourself knee- I is held. The screen which receives the image may be made of deep in one of those floating bogs which, the sportsman and I an oblong piece of glass either 44 inches by 34 inches, called by traveller may often unwittingly step upon in Ireland and else- I photographers a quarter-plate, or by a plate 5 by 4, according where, would youattempt to run and get out of it as quickly as 1 * "e •• - • - • ’ "