(and, above all, upon a single analysis) is no longer a complete scientific opinion. A water analysis henceforwards must be three sided, viz., chemical, bacterial, and microscopical; and even then the conditions of the origin and of the neighborhood of the source of the water must be included as factors of equal importance. The standard of water analysis has of late appreciably risen, and reports of "water analyses," if they are to fullfil the conditions imposed by the most recent progress, must include three different examinations, as follows: :

I. ENVIRONMENTAL, i. e., a more or less complete study of the source of the water, together with observations of the surroundings, and investigation of specimens unquestionably normal, from the vicinity.

II. CHEMICAL, i. e., the usual chemical analysis, with special attention, however, to the state of the nitrogen present.

III. BIOLOGICAL, i. e. (1), Microscopical, viz., a determination of the number, the species, and, as far as possible, the conditions of the larger microorganisms present; as well as of the masses of débris, etc.

(2) Bacterial, viz., a determination of the number, and, as far as possible, of the species of the living bacterial organisms present.

MEETING 393.

The History and Theory of Cohesive Construction as Applied Especially to the Timbrel Vault.

BY MR. RAPHAEL GUASTAVINO.

The 393rd meeting of the SOCIETY OF ARTS was held at the Institute on Thursday, October 24th, at 8 P. M., President Walker in the chair,

After the reading of the records of the previous meeting and the election of new members, the President introduced Mr. Raphael Guastavino, of New York, who read a paper on "The History and Theory of Cohesive Construction as applied especially to the Timbrel Vault."

Mr. GUASTAVINO first took up the history of cohesive construction, and showed by numerous examples that this construction was very ancient, and was not any particular invention, nor originated by any determined civilization, but was only the fruit of necessity. It reached the height of its splendor in the middle ages and gradually disappeared in the same proportion that modern civilization and the Renaissance approached. This decline was mainly due to the fact of the disuse of the hydraulic mortars of the Romans, Arabians, and Byzantines, and that the art of manufacturing these materials which constituted the base of their cohesive construction was lost.

The first time that cements were generally used in modern days was from 1845 to 1850. From this date commenced the renaissance of "cohesive construction."

The speaker said: The works of this character that I have constructed in Spain; as, for instance, the manufactory of Battlló, in the Corts de Sarria, where there are employed two thousand people with one thousand looms and 64,000 spindles, the other manufactories of Vidal, Muntadas & Co., and the woollen manufactory of Carreras, and the glass kiln of Cassademun with one arch of sixty-five feet span, with only ten-inch walls, and the cupola of the theatre of the town of Vilasár, of sixty-one feet span, are all permanent and durable buildings, the arches of which were built having the first two courses of plaster and the others with cement, representing 50 per cent of the construction with plaster, as I used in my first work in this country, where we knew that the excess of plaster was dangerous, if the walls and rods were not stout enough to resist the expansion. In some cases the risk and danger caused by the irregularity of the materials was so plain that the workmen were afraid, compelling me to remain in the works to inspire confidence and success.

The progress in Spain, particularly in Barcelona, in the special construction that we now have under consideration, was due to the studies and teaching of the professors who were debating for several years how to improve their respective specialties and the way to

obtain new practical systems of construction, knowing the fact that the improvement of the material required a change and improvement in the construction, but their noble aspirations were restricted, having no facilities, and it was necessary to satisfy themselves by recommending the theories of Vicard, about the use of cements, and other applications well founded.

Nothing was done about investigating these structures to which I have referred, and no coefficients were derived. This only can be obtained when we can depend upon the materials with mathematical regularity and with powerful apparatus for determining their reliability. In countries like this, where we can find more than twenty guaranteed brands of quick-setting Portland cement of different degrees, and where clay can be used for those constructions with advantage, and where we have regularity of manufacture, and finally in a country where we have powerful apparatus, coefficients can be obtained, as we have been doing for the past five years.

From these special advantages it seems that these works have culminated in the United States, taking a natural stand in New York and Boston, with specimens that have no rivals in any part of the world for lightness and resistance.

Cohesive construction differs from "mechanical construction" or the gravity system in that the latter is founded in the resistance of any solid to the action of gravity when opposed to the solid. From these conjunctive forces, more or less opposed to one another, the result is the equilibrium of the total mass, without taking into consideration the cohesive power of the material set between the solids, while the former has for a base the property of cohesion and assimilation of several materials, which by a transformation more or less rapid resembles Nature's work in making conglomerates.

The materials employed in the construction by gravity only require the physical quality of hardness; for the "cohesive construction" the materials must not only have proper physical conditions, but it is absolutely necessary to take into consideration the chemical properties of the substances employed.

Mr. Guastavino then had two arches of about 4 feet span constructed before the audience in the same way they are being made in the new Public Library on Copley Square. The centers are ordinary boards cut to the proper curve, on which is laid a course of bricks or

tiles about 12" x 6" x 1", the joints being of plaster of Paris. On the completion of the first course the centers are removed. The second course is laid in Portland cement, breaking joints with the first course, as is also the third course. The whole, after it is thoroughly set, forming a solid arch.

MEETING 394.

The Kriegsspiel as Practiced in America. Its Object and Place in Military Science, and its Relations to Military and

Naval Manæuvres.

BY MAJOR W. R. LIVERMORE.

The 394th meeting of the SOCIETY OF ARTS was held at the Institute on Thursday, November 14th, at 8 P.M., Mr. John C. Ropes in the chair.

After the reading of the records of the previous meeting and the election of new members, the Chairman introduced Major W. R. Livermore, U. S. A., who read a paper entitled "The Kriegsspiel as Practiced in America. Its Object and Place in Military Science, and its Relations to Military and Naval Manœuvres."

Major LIVERMORE said: Kriegsspiel in its present form is a device by means of which military operations are represented upon a map, the troops engaged being indicated by movable blocks. The movements are made, and the losses and other results of the conflict are determined, in accordance with established rules, which are designed to conform as nearly as possible to the conditions of actual warfare.

It has long been apparent that a faithful representation of military movements might form the basis of a most agreeable recreation, while affording at the same time an opportunity for students of mili

tary science to put in practice the principles and maxims which have accumulated in great numbers in the text-books.

The Kriegsspiel invented by Herr von Reisswitz, and elaborated by his son, an officer of the Prussian artillery, has met with favor among the Germans since the early part of the present century; and now that this indefatigable people has applied to the art of war the same exhaustive and systematic study that has proved so efficient in other branches of scientific inquiry, many of the results of its labors have become embodied in this game.

Outside of Germany for a long time the game was regarded with little favor. After the war of 1866, however, it was cultivated extensively in Austria, and the war of 1870 opened the eyes of all Europe to its importance. In the United States it has been practiced to a limited extent since 1867, and its popularity has increased with the reputation of the Germans as a military nation. It is now practiced extensively in Russia, Italy, France, Belguim, and elsewhere.

The Kriegsspiel is played upon a topographical plan, with small blocks representing the troops, which are proportioned to the scale of the map, occupying as much space upon it as the troops would occupy in the field. These blocks are moved simultaneously, under the direction of an umpire, and at rates proportioned to the mobility of the different arms which they represent.

When the position of the blocks indicates that the hostile troops are within sight and range of each other, they are supposed to open fire, if the players desire it, and in this case it becomes the umpire's duty to decide the result upon the basis of experience. The rules of the game explain to him how to estimate the loss from this fire; for example, it may have been found that, in similar cases, the number of killed and wounded has varied from ten to twenty; by throwing a common die he decides whether to assign a greater or a less result to the case in view. The rules of the game also explain to him under what circumstances troops have been dispersed by the result of fire, and what would be the probable result of a hand-to-hand fight. Since the time of Von Reisswitz the game has been much modified; and the different forms which it has assumed may be classed in three groups.

The first form lays down a few arbitrary rules based upon general results, and leaves the die to decide in each case when the