Being a constant reader of your valuable paper, and feeling a great interest, a real pock ei interest, m every thins; relating to leather, I real with more than ordinary interest, your article on this subject, in the Scientific American of the 4th inst. It has long been settled by one of tl,e wise men of the world, I may say, reduced to an axiom, that ' there is nothir-g like leather." But what is leather ? would seem to be a question yet to be solved. Webster defines it thus, " the skin of an animal dressed and prepared for use," which would seem to be p'ain enough,until youtuir. to his definition of ' tanning," which is, " the practice, operation, and art of converting the raw hides of animals into leather by the use of tan," which would seem to imply that "tan " was an essential ingredient in the production ot leather. This would seem to be Dr. Ure's idea, if I properly understand him, when he says, " it is the skin of animals, so modified bv chemical means as to have become unalterable by the external agents which tend to decompose it in its natural state." If tan or tannic acid is an essential ingredient in the production of leather, you will readily perceive that it is a misnomer to call the Preller" prjcess of softening hides and skins "tanning." Indeed I have no hesitation in saying that " tawing " is a much better term, by which to designate the " Preller " process ; as the vegetables you enumerate as constituting the compound used by htm, have little or no tannic acid in them; the minerals none at all. Least I should be considered captious, I will change my remarks to what may more properly be considered, the merits of the question, pertaining to this Preller process. You say it claimed that the leather produced by this procfss, is much stronger, and will wear much better." That the first half of the proposition, that hides and skins may be made tougher, by undergoing a process such as described, as that of Preller's, than if they were subjected to the ordinary tanning process, will not be denied by any one, who understands the art or mystery of tanning. No, it is an indisputable fact, that the raw skin is tougher than after it is manufactured into leather; that is, take two pieces of skin, o( given width and substance, the one tanned and the other raw ; and it will require a greater force to separate the raw than the tanned piece. So likewise is a piece of tawed skin tougher than a piece, ot tanned skin; but that it will ' wear better " lor the ordinary purposes for which leather is used, will scarcely be admitted by so old a member of the "craft" as I am. No we profess to change the material upon which we operate, by chemical means, so as to render it less alterable by the external agents which tend to decompose it, in its natural state; in short, to make it " wear better." The intelligent manufacturer and consumer wants something more than toughness in the quali'y oi his leatherhe wants suppleness, and the nearest approximation to impervious-consistent with a condition to permit the ready escape of perspiration ; that is, wants an article which, while it will let in the smallest amount of dampness, will offer the least obstruction to the escape oi that which is in. He wants an article about equi distant Iron) india rubber and Indian dressed or tawed (not tanned) buckskin or buffalo robes, a mean which 1 do not believe Mr. Prelltr, or any one else, can obtain from the use ot the materials designated in your article, as those used by him. While I shall be, or rather should be, much pleased, to hear of any real improvement, in the manufacture ot leather, from an expeiiinenter, upon the Preller pro ct-ss. I Irankly confess that I do not toi one moment anticipate such a result. S. S. Dayton, Ohio, June, 1853. [The author ot the above has experimentec a great deal in tanning, and is author of the patent piocess lavorably noticed on pages 288 ! and 289, ol Campbeil Moiiirt's work on the subject.