1869.] Modern Building Considered. 573 The above article was suggested by the following letter, from an esteemed friend : Philadelphia, Feb 2d, 1868, blttenhouse square. Samuel Sloan, Esq., My Dear Sir : In these days, when we are all excited over the recent disastrous fires, would it not be well to consider whether our buildings cannot be made more safe than the}' are at present, with very little ad- ditional cost ? You may remember the plan adopted in my house, and at the Washington Building, South Third street. In these instances, by casing the joints with thin sheet-iron, they were made so nearby fire-proof, that they will, I believe, at any time, resist the action of the flames sufficiently to pre- vent fire, of any ordinary description, burning through the floors fromJbeneath. I think it might be advisable to illus- trate this mode, in jtuu* valuable jour- nal, as well as the method adopted at the Harrison Building, on Spring Gar- den street, for securing the cornice to a parapet wall, so as to prevent fire coinmun-icatina: to the building from the cornice. You know the test the sheet- iron -cased joist was subjected to, pre- vious to my adopting the plan I have mentioned. If one disastrous fire is averted, by what you shall say, it will be sufficient reward for recommending this safeguard. Yours, very truly, Joseph Harrison, Jr. Galvanized Tinned-Iron. — One of the most remarkable advancements in the iron manufacture, in recent years, has been the introduction of galvanized tinned-iron, for an almost innumerable variety of purposes. This material con- sists of iron plate coated with tin, not by the ordinary tin-plate process, but by galvanic deposition. It serves as a sub- stitute for plain iron, for tin-plate, for zinc, and for lead, under certain special circumstances. It is stronger and more durable, for many purposes, than lead or zinc. It is better than plain iron, where rust is to be avoided. It is supe- rior to lead and zinc in warm climates, inasmuch as it does not expand and contract to so great a degree. Within- side a house and without, in vessels and in utensils ; in towns and in the coun- try •. in manufactures and in domestic economy, we now find this substance employed. We have galvanized tinned- iron, corrugated plates for roofing, and for the sides and doors of houses. In another form there are plain plates for the same purpose ; roofs for sheds, roofs and sides for storehouses, and many similar purposes. Then, besides the sheet form, there are round and square bars, hoop-iron, wire, tubes and pipes, nails, rivets, bolts and screws, all formed of iron thus protected b}' the galvano- tin process. There is this advantage, also, which is unattainable by the ordi- nary tin-plate process, that articles can be tinned after they are made in the proper form of iron, provided they are of small dimensions. The plates are really a combination of three metals ; for, in the first place, a layer of tin is precipitated on the iron plates, from a solution of chloride of tin, by the gal- vanic process ; and then a layer of zinc is obtained by clipping the sheets into molten zinc. Correction. The West Spruce Street Baptist Church. — In Vol. L, No. 4, page 244, third paragraph of our description of the above edifice, it is stated, that the dressings of the wall are of " Ohio Clough Stone." It appears through letters from Messrs. Worthington & Son, Messrs. Struthers & Son, and Mr. Wm. Appleton Potter, brother of the architect, that these dressings are really from the Worthington Quarry — at Brownhelm, Ohio — which affords a very superior kind of stone.
