In his proposed theory he assumes that the molecules of iron (say) contain magnetic atoms capable of motions of translation and of rotation. These tend to form closed magnetic circuits, but at ordinary temperatures are unable to do so on account of the close proximity of their centers. On raising the temperature their centers are further separated, till at about 680° C. their polar extremities rush together, forming complete circuits and exhibiting no external magnetic properties. On cooling down, the centers approach until the gravitation attraction overcomes the magnetic attraction of their poles, when the magnetic properties reappear. Prof. Ayrton asked whether the author had made experiments on the reappearance of magnetic properties when raised to a white heat, and Prof. Thompson inquired whether cobalt had been tested. Both questions were answered negatively. POISON OF THE SOMALIS, EXTRACTED FROM THE WOOD OF THE OUABAIO. The principle in question, ouabaine, forms rectangular plates, very slender, of a nacreous appearance. It is absolutely white, inodorous, and not appreciably bitter. It contains no nitrogen, and does not react with coloring matters. At a boiling heat, in presence of dilute acids, it is split up, yielding a reductive sugar. Its composition is C_{90}H_{45}O_{12}. It is poisonous if introduced into the circulation, but not if swallowed.--_M. Arnaud, in Comptes Rendus._ (Advertisements.) A New Catalogue of Valuable Papers Contained in SCIENTIFIC AMERICAN SUPPLEMENT during the past ten years, sent _free of charge_ to any address. MUNN & CO., 361 Broadway, New York. * * * * * THE SCIENTIFIC AMERICAN Architects and Builders Edition. $2.50 a Year. Single Copies, 25 cts. This is a Special Edition of the SCIENTIFIC AMERICAN, issued monthly--on the first day of the month. Each number contains about forty large quarto pages, equal to about two hundred ordinary book pages, forming, practically, a large and splendid =Magazine of Architecture=, richly adorned with _elegant plates in colors_ and with fine engravings, illustrating the most interesting examples of modern Architectural Construction and allied subjects. A special feature is the presentation in each number of a variety of the latest and best plans for private residences, city and country, including those of very moderate cost as well as the more expensive. Drawings in perspective and in color are given, together with full Plans, Specifications, Costs, Bills of Estimate, and Sheets of Details. No other building paper contains so many plans, details, and specifications regularly presented as the SCIENTIFIC AMERICAN. Hundreds of dwellings have already been erected on the various plans we have issued during the past year, and many others are in process of construction.