TRANSACTIONS OP THE SECTIONS. 59 



I have to acknowledge the assistance of several friends. Members of the Leeds 

 Photographic Society, of whom some worked conjointly with me, and of others who 

 freely communicated to me their experience in working the albumen process. 



The modification of tlie original process which I have adopted, consists, first, in 

 using only one bath for both the first and second sensitizing of the plate. This bath 

 is composed of about 35 grains of nitrate of silver per ounce, witli about 10 per cent, 

 of the commercial acetic acid known as Beaufoy's acid. Secondly, in nsing a very 

 fluid collodion somewhat highly iodized and not containing any bromide, and in using 

 albumen without any other addition than a bromide and sufficient water for its solu- 

 tion. I use about 4 grains of bromide of potassium for the white of each egg, but 

 the particular bromide, or the precise quantity, does not appear to be very material. 

 And, thirdly, in drying the coating of albumen by suspending the plate in a wire 

 cradle attached to a long thread over a heated iron plate, and keeping the prepared 

 glass plate in rapid rotation until dry, so as in the first instance to throw off the 

 superfluous albumen by the centrifugal force, and then to cause the plate to dry 

 equally from the centre. 



I use a similar method of drying after the second sensitizing, but without heat if 

 the plates are to be kept more than a day or two. 



By adopting these manipulations, I have been able to prepare plates up to 1 7 inches 

 by 13 as free from blemishes and with very little more trouble, than if collodion alone 

 had been used. 



I have always preferred to develope the picture by gallic acid, using a cold, nearly 

 saturated solution, with the addition of about 4 minims per ounce of a solution of 

 nitrate of silver, 30 grains per ounce with about 30 minims of acetic acid, i. e. rather 

 less acidified than the bath solution. This generally developes the picture in about 

 an hour and a half; but if the picture be faint from over-exposure, or slow in developing 

 from under-exposure, an addition of double or treble the quantity of aceto-nitrate 

 solution should from time to time be added. A greater quantity of silver in the first 

 instance appears to retard the development. 



Small plates may be more speedily developed by pyrogallic acid, but with large 

 plates I find gallic acid preferable, both on the score of economy, and that with pyro- 

 gallic acid constant care is required in watching the development and in preventing 

 the spoiling the result by a muddy deposit. 



The theoretical advantages of this process appear to me to be, that, compared with 

 other processes, it permits quite as great, and I think a much greater latitude in the 

 time of exposure ; that whilst the rapidity is as great as can be desired (except for 

 the instantaneous efiects, which are only practicable with wet collodion), an exposure 

 for many hours or even days may be given for feebly illumined objects ; that the use 

 of an iodide in the collodion and a bromide in albumen, give a great increase of sen- 

 sibility, in like manner as the accelerating effect by the alternate use of iodine and 

 bromine in the Daguerreotype; that the image is formed on the plane on which the 

 combined films of collodion and albumen coalesce together, and where alone there is 

 a combination of iodide and bromide of silver; thus, although it is necessary that the 

 plates should be very carefully cleaned to prociue the perfect adherence of the film 

 of collodion, neither impurities on the surface of the glass plate, nor on the upper sur- 

 face of the albumen, are increased during the development of the image ; that the 

 drying the plates by heat prevents almost entirely the blistering of the plates, which 

 has been found so great a disadvantage in the process as published by M. Taupenot. 

 Note. — Subsequent experiments have shown the use of a bromide alone in the 

 albumen to be fallacious. 



On a New Process for Making and Melting Steel. By P. J. Worsley. 

 This process, invented by Dr. Gurlt, is interesting as an example of the method of 

 applying fuel, known as the gas-fuel method, by which the useful portions of the fuel 

 are brought to bear while all impurities are left behind. This latter advantage is 

 peculiarly applicable to iron and steel making, as the chief impurities in these metals 

 are derived from the fuel. Dr. Gurlt exposes iron-ore to a current of gas, of which a 

 small proportion is burnt to give the necessary heat. A short exposure merely reduces, 

 a longer carbonizes, so that either malleable iron, steel, or cast iron can be obtained 



