W. B. N., Mexico--Mr. N. says--"Will some of your subscribers give, through your Journal, a practical and first-rate process for producing Calotypes?" We hope some of our "subscribers" will furnish the same. H. B. T., Ohio.--Mr. T. says--"Will you give a ready and easy method of detecting chlorine? I find in a former number of your valuable Journal, that you have been making experiments with this gas. I have had remarkable success with this gas, although not a practical Daguerreotypist." Mr. J. will find 'this gas' is readily distinguished from other gases by its color, odor, and bleaching properties. Probably the most simple method of detecting free chloride is to hold a rod dipped in aqua ammonia over it, when white fumes will be formed. Will Mr. J. have the kindness to forward to us his experiments--we would like much to lay them before our readers. A Stock Dealer, in one of the Southern States, writes--"What articles of stock will be less needed by artists, provided Mr. Hill's process proves true, of producing pictures with all the 'colors of nature?'" _Colors and brushes!_ J. W. S , Mich.--We forwarded the article you ordered, and enclosed the balance in the package. The view camera you had better order soon, as it will be some time before Mr. Harrison can get it ready, he having so many orders now on hand. You had better have one of Lewis's _new_ Camera boxes. T. J. C., Va.--We cannot recommend the articles you speak of; they involve only an old vague principle, and are only worthy the person having them in charge. A. G. L., Pa.--The money received and forwarded to Europe--your plan may work, but it looks a little too "opaque." You will find by heating an iron plate, and applying it to your apparatus, will facilitate the operation much. Chapman has the exclusive right to the patent. E. W., Miss.--See page 24, Daguerreian Journal. R. M. H., Ala.--You will find "Silliman's Journal" a great aid and valuable work, published the first day of every second month, price $5 per year. New Haven, Conn. See answer to L. I. G., page 187. * * * * * NOTICE OF NEW PUBLICATION. The New York Register of Medicine and Pharmacy, published semi-monthly and edited by Dr. C. D. Griswold.