Kitabı oku: «Chambers's Journal of Popular Literature, Science, and Art, No. 688», sayfa 3

Photography as now practised may be classed under two general heads – the wet process and the dry process: the first being solely dependent upon the use of collodion and the silver bath; the other dispensing with either or both. Hitherto, the great obstacle to the landscape photographer has been the cumbrous nature of the impedimenta necessary to the production of pictures at a distance from home. It is by no means an easy matter to transport a dark tent containing a chemical laboratory, together with a camera and the necessary supply of water, from one place to another. Moreover, the scenes which naturally tempt the artist lie in unfrequented, and oftentimes in almost inaccessible places. The use of dry plates, by which the necessity of a tent is altogether obviated, has rendered the art far more easy of accomplishment, and has thus placed outdoor photography amongst those pastimes which a non-professional can successfully pursue. In the wet process the sensitive collodion plate must be exposed to the air within a very few minutes of its removal from the silver bath, otherwise it becomes quite useless; the object of the various dry processes being to preserve the film in a sensitive state, so that it can be exposed as occasion may require, and developed in the studio at a future time. It is needless to point out that this method of photography dispenses at once with any travelling gear except the camera and lens, and a convenient light-tight receptacle for the sensitive plates. Many ingenious contrivances are now used in the form of changing boxes – as they are called – by which plates may easily be transferred to the camera without danger of exposing them to any accidental gleam of light. The jealousy with which a tourist naturally guards his treasured dry plates has more than once roused the suspicions of the acute Custom-house officer, who, in his zeal for the welfare of the revenue, has unwittingly spoilt the produce of many days' careful work, by insisting upon opening the strange-looking box!

Although it would be beyond the scope of this paper to enter into detailed explanation of the manner in which dry plates are prepared, the importance of the subject must claim some attention at our hands. In order to render a collodion plate capable of being kept indefinitely in a dried and sensitive condition, it is found that a solution of some organic substance must be washed over it, and dried with it. To enumerate all the various agents that have been employed for this purpose, would be impossible. Tea, coffee, sugar, tannin, gum, gelatine, with many other compounds, have each found favour with different experimenters, and with varying success; but the last-named substance, gelatine, is perhaps likely to supersede all the others, as giving more satisfactory and constant results. Plates thus prepared, although almost wholly disregarded by the professional artist, have, on account of their portable nature, a large sale among the amateur members of the photographic world. They are also almost exclusively used in astronomical photography, a branch of the art to which we will now direct the reader's attention.

It will be remembered that on the occasion of the last eclipse of the sun, expeditions to observe it were sent out from nearly every country of the civilised world; each expedition depending largely upon photography as a means of recording its labours. Although the state of the weather at many of the selected stations rendered the apparatus useless, a great number of pictures were actually obtained, a comparison of which set at rest certain theories relating to appearances which had up to this time been the subject of much discussion and speculation. No human hand could have correctly depicted such an ever-varying object as the sun presented at this time, to say nothing of the well-known fact that the power of correctly estimating appearances varies so much with individuals, that a comparison of mere drawings would be quite useless for the purpose in view. The cause of the periodical changes in the sun's spots yet remains to be discovered; and it is probable that the photographs which are being almost hourly taken (having for their object the solution of this problem) will ultimately lead to a satisfactory result.

The transit of Venus represents another important field of inquiry in which photography has done useful work. The expeditions fitted out two years ago, with their splendid array of modern instruments, would compare strangely with the preparations for the investigation of 1761, when Captain Cook started on his ill-fated voyage to Otaheite. Still more vivid does the progress of scientific research become when we remember that the very first observation of the transit of Venus was made one hundred years earlier, with no better apparatus than a bit of smoked glass. When we consider that the main value of such an observation rests upon the appearances recorded at the moments of ingress and egress of the planet upon the sun's face, the importance of a means for securing instantaneous pictures will be appreciated. It is true that certain optical defects exist in these pictures which prevent their use for the purpose of reliable measurement; but these obstacles, we trust, may be overcome by 1882, when the next transit will be due.

The practice of micro-photography – that is, a combination of the camera with the microscope – has lately met with some attention among scientific men, and there are now many workers who are trying to bring it into the prominence which it deserves. Formerly, drawings of microscopic preparations could only be secured by means of a prism (or camera lucida, as it is called), fitted on to the eyepiece of the microscope, by which means an enlarged spectral image of the object became apparent on a sheet of paper placed near the instrument; the lines thus exhibited being rendered serviceable by the careful use of the lead-pencil. It is obvious that such means afforded a very imperfect representation of the image as it really appeared in the field of the microscope, even if the operator possessed some amount of artistic skill; but now, by the aid of the camera, a picture of the most unfailing accuracy can be secured in a fraction of a second. Such rapidity is only required, however, where the object is of a fluid or animated nature, as in the case of moving organisms. We venture to think that there is a great future in store for micro-photography.

One of the most recent applications of photography to scientific uses is exemplified in its adaptation to the spectroscope, by which we are furnished with evidence of the composition of the heavenly bodies. Any account of this marvellous device we must, however, leave for a future paper. In the fine and useful arts, photography now plays an important part. Portraits, life size, executed in oil, are successfully painted from small photographic likenesses, at a comparatively small cost; and with this important advantage, that the likeness in every case is unchallengeable. This may be considered a great triumph in the photographic art.

This power of enlargement to any reasonable dimensions is a great addition to the resources of the photographer; and it is not alone confined to portraiture, as the numerous large-sized landscapes constantly exhibited will testify. In former times, when the lenses then in use were capable of including but a small portion of a view, the only way to secure large pictures was to take them in sections, and afterwards to join the paper prints. The lines of junction were naturally a great disfigurement to the finished result, to say nothing of the extra labour which such mode of proceeding involved. The impossibility of preserving the exact tone of colour in these different sections through all the vicissitudes of printing, toning, and fixing, was also enough to condemn the process. These difficulties have been altogether obviated by the construction of lenses which will include any amount of the view before which they are placed, and which moreover give a picture so perfect in detail as to admit of being greatly magnified without injury to its beauty. The enlargement is now carried out by a copying camera of the form of the well-known magic lantern, and lighted by an oxy-hydrogen or magnesium burner. The negative takes the place of the ordinary painted slide, and the enlarged image is projected upon a sensitive surface.

Perhaps the greatest problem which the photographer has to solve is the production of landscapes with their natural canopy of clouds. This difficulty will be understood when we explain that the sky being such a brilliant object, requires but a very small fraction of the exposure which is demanded by the grass and trees beneath it. The plan generally adopted is to secure a separate negative for each of these component parts of the picture, and to join them mechanically previous to the operation of printing. The beautiful instantaneous marine studies which we all admire – and which represent the clouds in every variety of form – are produced without this double exposure; for it is obvious that the reflective property of water confers equal brightness on all parts of the view.

The production of photographic pictures in printing-ink by means of the press is now receiving a great deal of attention. Most of the processes adopted owe their origin to the effective mixture of gelatine and bichromate of potash. It will be necessary to explain that the gelatine so treated is not only – after exposure to light – rendered insoluble, but it becomes quite non-absorbent of water. This property is taken advantage of in the following manner. A thick plate of glass or metal coated with the mixture is exposed under a negative, and afterwards placed for a time in cold water. It is then found that those parts of the plate which represent the lights of the picture remain flat; whilst the other portions which have been protected from the light swell up into high-relief. The plate can then be rolled with ordinary printing-ink, and impressions taken to any reasonable amount.

Space will not permit us to detail the various modifications of this process which exist under different designations. Metal plates can now, by a very similar treatment, be made ready for the etching acid. Wood-blocks which no artist but the sun has touched, can be given to the engraver ready to his hand. The lithographic printer is also independent of the draughtsman, for absolutely perfect fac-similes of maps, plans, &c.; line-subjects can also be produced in endless quantity.

The applications of this wonderful art are already legion, and are so continually receiving additions, that we may hope that its sphere of usefulness will be extended beyond all present calculation. As a means of livelihood for thousands, its importance in a commercial sense is invaluable, while as the handmaid of the philosopher, it fulfils a higher duty, in helping us by sure and certain steps to the attainment of scientific truth.

THE LAST OF THE HADDONS

CHAPTER XI. – CROSS-PURPOSES

Our journey back to Fairview was a very silent one. Under the plea of being tired, Lilian lay back in the railway carriage with her eyes closed and veil down. I did not disturb her, and for the best of reasons: I could think of nothing very cheering which could be honestly said. Marian Reed was an unpleasant fact, which could not be argued out of existence, nor even smoothed over by all the words in the dictionary combined. The carriage was waiting for us at the railway station; and only just as we arrived at Fairview did I venture to speak: 'Are you going to tell Mrs Tipper to-night, Lilian?'

'Yes. And you will help me, will you not, Mary? I shall depend upon that;' clinging closer to me, and feeling, I knew, terribly in need of help.

'Of course I will, if you wish it, Lilian. But I must stipulate that you first come to my room and rest for an hour.'

She obeyed me like a child – utterly worn out in spirit, holding my hand fast in hers as she lay on the couch, and murmuring every now and again: 'Help me, Mary; don't leave me.' 'Since I have promised, I suppose I must, my dear,' I replied in a rallying tone. 'But I do not generally care much about helping people who do not help themselves.'

She yielded to a burst of tears.

'That's better, dear – far more sensible,' I remarked, wiping my own eyes: 'one generally gets on more comfortably after availing one's self of that privilege.'

'Privilege?'

'"Right," if you prefer the word; one of our rights. If one could attain the end by more dignified means, it might be as well; but the grandest of heroines occasionally shed tears; so I suppose it is the best known method of making one's self comfortable; and harmless enough when used with discretion – as heroines use it.'

'Ah, Mary, you are not talking like yourself. When you talk like that, I sometimes think it is to conceal' —

'Well, dear; why do not you go on? To conceal what – that I am not a heroine?' I asked in a jesting tone, only too glad to be able to draw her sufficiently away from painful reflection for a little nonsense-talk.

'I sometimes think that having larger needs than other people' —

'Well, dear?'

'Which needs have not been satisfied' —

'There is something still required to make a complete sentence, you know.'

'Are large needs ever quite satisfied, Mary?'

'Dear Lilian – dear sister – perhaps not.'

'Mary, you said sister!' A soft flush in her face, and eager love in her eyes.

'Because I meant it, I suppose, dearie; I can give no other reason,' I said, trying still to keep the jesting tone. 'If you do not object to an elderly sister?'

'Not if elder sisters do not put themselves out of reach of the sympathy of the younger.'

'Put themselves,' I repeated musingly. 'May not circumstances do that for them?'

'When will you tell me – dear Mary, when will you let me feel that you really are like a sister to me?'

At which I morbidly shrank back into my shell again. 'When my love-story is finished you shall hear it.'

'Finished! As though a love-story ever could be finished – as though you or I would care to have one, if it could! But you have not told me even the beginning.'

'You have found out that for yourself, darling.'

'And am I right in thinking – I hope I am not; but – Dear Mary, am I to say exactly what I think?'

'Exactly.'

'Then sometimes I think that one you loved – Mary, is he dead?'

Dead! Philip dead! I laughed in spirit. If he were dead, should I be alive – in this way? I did not reflect that my silence and the few tears which stole down my cheeks might seem to bear out her theory as to my having something to regret. But I presently shook myself free of sentiment, smilingly observing that we could not afford the luxury of analysing our feelings just then. Sentiment would be only a stumbling-block in our way, when we needed all the nerve, courage, and steady self-control we could muster.

'To begin with: would you like me to make matters smooth and pleasant with Mrs Tipper before dinner, Lilian? You would then perhaps find less difficulty in broaching the subject to Mr Trafford, if, as I fancy, you prefer doing so in our presence?'

'Yes; I do prefer that, ever so much; and I shall be glad if you will tell auntie, Mary.'

As I had anticipated, we found no difficulty in bringing the dear little lady to our way of thinking. As soon as she had in some degree recovered her astonishment at the revelation, she expressed her entire approval of what had been done. She was not a little shocked and distressed to find her brother had been less perfect than she had imagined him to be; but it appeared to her a natural and right thing that Marian Reed should be asked to come to reside at Fairview. Even my little 'aside,' which I thought necessary, lest her expectations should be unduly raised, to the effect that we did not as yet feel quite sure Marian would be a desirable person to live with, had no weight with Mrs Tipper. She could only look at the question from one point of view – whether it was right to do as Lilian had done. Whether the other would be more or less pleasant to get on with, was, in her estimation, beside the matter. There were no more complications in Mrs Tipper's estimate of right and wrong, than there were in her niece's.

Our real difficulty was to come; and although she said no word about it, I knew Lilian felt that it was. Arthur Trafford was dining with us; he very rarely missed coming since Mr Farrar's death. But it was not until after dinner, when we had returned to the morning-room (we all preferred its cosiness to the drawing-room splendour, now), that the subject was approached. In reply to her lover's question, which had been asked more than once during dinner, and was now repeated, as to how she had got through the day, Lilian drew nearer to me and murmured: 'Mary and I went to town, Arthur.'

'To town! What for? Why in the world did you not tell me you were going? It was not like you, Lilian, to say no word to me about your intention last night;' with, I fancied, a rather suspicious glance towards me as he went on: 'I do not like the idea of your running about like a mere' —

She looked very pale, seeking, I think, in her mind for the best way of commencing.

'I was obliged to go; and you must try not to blame me for having said nothing about it to you first, Arthur,' she said, in a low tremulous tone, which I saw flattered his vanity, as proof of his power, and the timid yielding spirit, which he was pleased to think so characteristic of her. Not that he wished her to be timid and yielding to any one but himself; or was ready to make sufficient allowance for her acting according to her nature, upon all occasions.