gas. It is a liquid which is dispersed by detonation, or, more recently, it is arranged to be sprayed by aircraft with great effectiveness. It does not remain dispersed but settles out quickly. It is a most effective agent of either defense or offense. Its chief value is as a vesiccant, producing serious burns to one not protected against it.
Asphalt and Steel Pavement to Be Tried in Paris. ~urfastal,a new pavement laid under British patent, and aldady said to be a success in England, is soon t o be given a trial in Paris, according t o advices from Consul Raymond Davis, Paris. The Socidtl Surfocier, the company holding the rights to this process in France, claims that the pavement is particularly adapted t o city uses. It maintains tbat ordinary asphalt and concrete pavements, although greatly improved in quality during recent years, are still incapable of standing up satisfactorily under certain conditions, as, for example, a rapid and intense circulation, the stops and departures of heavy autobuses, sharp turns, and heavy loads. Surfastal, as it will be laid in Paris, will consist of a concrete foundation about 6 inches in thickness, upon which is poured a 0.5-inch layer of asphalt. A steel trellis or framework is then placed upon the asphalt, composed of strips 1 inch in height, 0.125 inch in thickness, and forming squares of about 5 inches on the side. To prevent displacing before completion of the surface, each square is connected by steel pins. When this trellis has been set in place, the squares are filled with asphalt and the resulting surface is thus divided into a series of small squares, bounded on each side by strips of steel, connected by steel pins. Since the framework is sufficiently flexible to conform to the profile of the foundation, it becomes an integral part of the wearing surface. The weight of heavy loads, therefore, is suppo9ed by the steel framework distributed over a considerable surface area, and the wear on the asphalt is nevcr more than the wear on the edge of the steel strips, thus reducing maintenance cost t o a minimum. When asphalt or concrete is used in the surface layer, the material contained in each square extends under the steel framework t o the contiguous squares and forms a homogeneous mass, separated an the surface only by the steel strips to a depth of 1 inch. While Surfastal could, of course, be employed for entire sections of city pavement, it would appear t o be of the greatest value for certain specified uses.-Ind. Eng. Chem., 21, 125 (Feb., 1929). Commercial Uses for Bentonite. As a result of investigations conducted by the Bureau of Mines, it is announced tbat extensive commercial uses will probably be found for bentonite, one of the oldest and least known mineral substances. Certain bentonites have such strong affinity for water that they are capable of absorbing more than ten times their volumes of water. Owing t o its peculiar physical properties, bentonite as a component material in the manufacture of commodities as has been suaaested ~. d~verrified3s rmlwr. ruhh'r, putty, phonuxraph records, pencil leads. and swaps On the orhrr hand. undernruund drposits of hentonite h a r e r x w d great diffirultir* in the drilling of oil wells, it frequently becoming necessary t o take special steps t o combat the nuisance. Bentonite contains 75 per cent or more of the crystalline clay-like minerals, montmorillonite or beidellite. A largenunlber of samples of hentonites from many sections of the United States were studied in the course of the investigation.-lnd. Eng. C h m . , 21, 133 (Feb., 1929).
