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PHOTOGRAPHIC PROGRESS.

It is doubtful whether any industrial art has made such rapid strides within the last thirty years as that of Photography. Founded upon the simple discovery that a certain chemical salt—the chloride of silver—becomes blackened upon exposure to light, the art has grown step by step into an important national industry. It would be next to impossible to estimate the number of persons who, directly and indirectly, owe their daily bread to King Sol in his character of Artist. A glance at the advertisement columns of one of the journals devoted to this interest will give us some idea of the busy number of camp-followers running in the wake of the huge army of photographic artists of Great Britain alone. Opticians, paper-makers, chemical manufacturers, glass-makers, cabinet-makers, besides a host of others who supply the et-cæteras of the business, vie with each other in the adaptability of their goods. Other countries can no doubt shew a similar list—notably France, whose paper is used by photographers throughout the world.

Although the peculiar affinity of silver chloride for light was discovered by Scheele just one hundred years ago, its application to art was not recognised until the year 1839, when Daguerre in France and Talbot in England almost simultaneously hit upon the method of rendering permanent the pictures which had been before obtained, but which had faded away into darkness as quickly as the daylight which had given them birth. This discovery of fixing the image, as it is technically called, was really the starting-point of an art, samples of which, good, bad, and indifferent, are now to be found in every homestead in the kingdom.

The mysterious power which could seize almost instantaneously the fleeting appearances of moving life, could not fail to take a strong hold on the public attention. Other art-pursuits had of course previously had numerous aspirants, but they came and went as fashions do, without leaving any permanent good behind them. Not so photography, which is perhaps unique in owing its present state of perfection to the exertions and patient investigations of mere amateurs. The reason of this unusual state of things is probably due to the fact that photography has required a large expenditure of both time and money to bring it to maturity; both which commodities are more plentiful with those who have not to work for daily bread.

The earliest sun-pictures, as produced by Daguerre, and named after him, were formed on silver plates treated with iodine. After exposure in the camera, they were developed by the action of mercury vapour, which attached itself to those portions of the plate which had received the greatest amount of light. Such pictures were necessarily difficult of multiplication, each impression requiring a separate exposure and development. Examples of this early method of photography may still be seen in many houses, where they have been carefully treasured as mementoes of friends who have passed away. These pictures are by no means of a permanent nature, the action of the air contributing with other causes to tarnish the silver plate, and so gradually to destroy the image thereon.

The discovery of the collodion process by Archer in 1851, quite supplanted the previous method, and gave photography an impetus which has carried it rapidly forward to the present date. Numerous substances have been tried at different times to support mechanically the delicate sun-printed image, but nothing has as yet been found to equal collodion upon glass.

Photographic art has now become such a thing of our every-day life, that perhaps there is scarcely an intelligent person who does not know the difference between a negative and a positive. Every one nowadays has his or her portrait taken at least once, and can well remember the nervousness incidental to a first visit to the photographic studio. Usually the photographer is kind enough to allow his anxious client a glimpse of the picture in its earliest stage, when the lights are where the shades ought to be, and vice versâ. Such is the negative, from which any number of positives may be printed by the action of sunlight on prepared paper placed underneath it. These silver prints (for although the silver plate is banished with the old method, chloride of silver contained in the pores of the paper still holds its own) have unfortunately the character of not being as permanent as they might be. This fault is commonly attributed to carelessness in not thoroughly eliminating the salt used in fixing the pictures; so that, by a strange anomaly, the discovery which claimed to make our photographs permanent is now charged with the sin of causing their ultimate deterioration. Photographers complain that the great competition, which has led to the adoption of low-priced work, will not permit them to give to the washing of the prints the time and attention which permanence demands. There are no doubt other causes at work in our heavily charged town atmospheres which have a destructive effect on our photographs. At anyrate, be the cause what it may, it is the rule and not the exception to find a paper print of, say ten years old, sadly faded and generally disfigured. Such a great disadvantage as this has met with an antidote in the shape of a discovery which has to a certain extent superseded the practice of silver printing. We allude to the carbon process, which is dependent upon the curious fact that bichromatised gelatine, after exposure to light, becomes insoluble. That is to say, a mixture of gelatine with the bichromate of an alkali—such as the bichromate of potash—will remain soluble so long as it is excluded from light. Carbon in the form of lampblack, or indeed any pigment, is mixed with this bichromatised gelatine, and paper coated therewith is exposed under a negative in the same way as in the case of a silver print, warm water being afterwards used to wash out those portions of the prepared surface which the sunlight has not rendered immovable.

Such, briefly, is the mode of producing the so-called carbon pictures, which without doubt are, as they claim to be, as lasting as the paper on which they are printed. They are not equal, in point of brilliancy, to the better known silver pictures, but this disadvantage is more than counterbalanced by their good keeping qualities. The word carbon as here used is a misnomer, for as we have already indicated, other pigments, most of which have a metallic origin, may be used in the process.

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