_Difficulties in the Wax-paper Process._--Can any of your photographic correspondents give me some hints regarding the following difficulties, which I (in common with many other amateurs) have met with in working according to Le Gray's wax-paper process? The proportions I used were exactly those published by Le Gray, and the paper and other materials were of the description he recommends; but nearly every picture, on being placed in the gallic acid, was spoiled, by the appearance of numerous small black spots, all well defined on one and the same side, but comparatively undefined on the other. These may possibly have been owing to iron in the paper, and may therefore, perhaps, be obviated by following the method of MR. CROOKES. But I am anxious to learn if others have experienced these spots in their pictures, and to what they attribute them, as well as how they can best be prevented. My second difficulty was in the want of intensity in the pictures, which completely prevented my obtaining even a tolerable impression from them. I tried many different times of exposure, and even after working long with Le Gray's slightly-different proportions, but always without success. The margin of the pictures, however, which had been exposed to the daylight, always became of the _most intense black_, after the picture had been developed. But my third difficulty was the most annoying of all, because the constant source of failure, though in itself apparently the most easily obviated. It was the difficulty of keeping the dishes which contained the solution _clean_; the effect of this want of cleanliness being the _marbling_ of the pictures whenever placed in the gallic acid and aceto-nitrate of silver. This is a difficulty I never before encountered, during half a dozen years' practice of photography (during which I used to be as successful as most of my brother amateurs); and though I tried every plan I could think of to insure cleanliness, such as washing the dishes with warm water, nitric and muriatic acids, &c., and afterwards wiping them thoroughly with clean cloths, still the mixture of gallic acid and aceto-nitrate of silver, for developing the picture, brought out some marblings or blotches on the dish, which were invariably communicated to the picture, even though it was only floated on the surface of the solution, and prevented, with the greatest care, from touching the bottom of the dish. Should the dishes be kept in the dark constantly? Have any of your correspondents tried Le Gray's plan of filtering the nitrate of silver through animal charcoal; or do they find any occasion to filter at all? With me, the animal charcoal seemed to increase the sensibility greatly. G. H.