Photolitho.—We are aware that Mr. Woodbury has so altered his process as to get rid of the necessity for using a preliminary coating of collodion. He now prints on the bare gelatine, and after exposure mounts the film, sensitive side downwards, on a plate of glass coated with gelatine and chrome alum.
Portraits by the Magnesium Light.—Mr. W. G. Lewis has sent us some carte portraits taken at night by the magnesium light, which show that in his hands this neglected branch of photography is very successfully managed. The faces are full of delicate half-tone. The time of exposure was three times that required in ordinary daylight.
George Thompson.—1. Although we do not esteem the maker of your lens as one of the best, he has, for all that, a fair reputation in his own country; and we know that he has made some good lenses. We have not, however, heard of him for several years past.—2. Dr. Monckhoven is a dealer in apparatus—not a manufacturer of lenses.
F. C. S.—Ideas often run in parallel grooves. For several weeks past we have been using our note-book very freely in the collection of materials for such a series of articles as that suggested by you. Some of the information required to render the series of the greatest possible value is only procurable with much difficulty and at no little expense; still, such progress in the compilation has been made as will warrant the indulgence of a hope that we may be able to introduce the subject at no distant date.
Erratum.—In Mr. Coote’s article in our last number, page 38, second column, eleventh line from top, for “you are apt to hurry and free the development,” read “FORCE the development.” Mr. Coote also informs us that in the middle paragraph of the first column in the same page, a sentence there in which he gave his reason for discontinuing the use of the salt bath for washing the plates will read better and more correctly as follows:—“Firstly: I found the extra salt bath and long washing required after it to considerably lengthen an already sufficiently tedious method of preparation.”
Subscriber.—Excuse plain speaking, but your pictures are by no means good—in fact, they are very bad. We are at a loss as to what to attribute their special qualities—whether to want of care or want of knowledge and experience. Carelessness, to all appearance, has had much to do with the matter; for the plate has been badly coated and is torn, and the developer has not flowed smoothly over the surface. After you have acquired some more experience and dexterity in manipulation write again, enclosing a specimen. You need not entertain any fear of your name and address being divulged.
W. K.—No more easy and expeditious method of collecting oxygen in a bag can be adopted than that which has so often been described in our Almanacs and Journals, viz., connecting the bag with the washing bottle by means of an india-rubber tube, the bottle being in turn connected with the retort in which the oxygen is generated. The method of making oxygen from chlorate of potash and black oxide of manganese is the simplest, cheapest, and best to adopt when only a small quantity is required. By a small quantity we here mean such a quantity as will be required by a professional enlarger of photographs in full practice.
Sam Weller says—“1. Can you inform me what the method is for enlarging designs for calico or zinc plates to be engraved for the purpose of tracing from by pentagraph?—2. Also as to the manner of building a suitable glass house, and kind of light—north or south?—3. Also, if a cheap condenser for the solar camera may be made by cementing a clock glass to a plate of sheet glass and filling it with water?”——We reply:—1. A design can be placed upon a zinc plate by the combination of enlarging and photolithography, or by transferring a carbon enlargement.—2. A north light is better than a south; for the rest, it will be necessary to consult an architect.—3. This query is answered with some degree of minuteness in the first paragraph of page 30 of our Almanac for the present year.
Old Harry asks—“What is a pistolgram?” We are to some extent ashamed of the definition we are about to give, but we can offer no other. It is a small picture taken by a pistolgraph, and this, in turn, is a small camera introduced by Mr. Thomas Skaife, by which photographs might be taken with a very rapid exposure. We strongly suspect that “Old Harry” knows more of the subject than he wishes us to believe, otherwise why put the question concerning the greater angularity of aperture that is possible to be obtained with a short than with a long-focus lens? and to which we reply that, without at present speculating on the cause, the effect is just as he states it to be. The same principle applies to the object-glasses of microscopes, and it is an important element in the recognition of object-glasses of the highest quality.