The plant that Mr. Webster has built at Crossness to test his system is only relatively experimental, having a capacity of 500,000 gallons a day, and by extending or enlarging the shoots, 1,000,000 gal. lons, for which there is sufficient room and power. At 30 gallons per head per day this would be ample for a town of 30,000 inhabitants in England. In the United States the sewage is larger in quantity but more dilute, requiring larger shoots and more iron surface, i. e., a somewhat greater first cost but about the same operating expenses. In England the cost of a 1,000,000 gallons a day works, with duplicate engines and dynamos and iron plates lasting ten years, is estimated at $30,000, or $1 per inhabitant, but would be materially less here, if the cost of steam and electrical machinery and contract construction work in the two countries furnishes any basis for comparison. The expense of 300 pounds of iron daily consumed has been estimated in the cost of the plant, and the labor of four men and the consumption of a ton of coal or less make a daily expense of $13. A visitor at the station is invariably impressed with the success of the system, no unpleasant odor is perceptible, and the appearance of the sewage during treatment and precipitation is far more inviting than the surface of the streets of the crowded parts of even Boston. The epicures of London may be looked upon as opposed to this system, for, according to Lawes, the fish of the Thames feed on the sewage; and where will the tempting and luscious whitebait, that is now taken only in the Thames estuary, and for which the cuisines of London are famous the world over, find its food and the dredgers find employment if the crude sewage is successfully treated by the electric current?

The paper was illustrated by numerous diagrams and lantern views.

The 400th meeting of the SOCIETY OF ARTS was held at the Institute on Thursday, February 27th, at 8 P.M., Prof. R. H. Richards in the chair.

After the reading of the records of the previous meeting the chairman introduced Lt.-Com. J. G. Eaton, U.S.N., who read a paper on "Domestic Steels for Naval Purposes."

Mr. EATON said: Within the scope of this paper lies properly a rapid retrospect of the history of domestic steels, with a view of understanding fully the marvelous development that has occurred within the past seven years. The uses we are to consider are those strictly germane to ships of war, and include not only hulls and hull material, but boilers, engines, rigging, guns, and armor.

Proceeding in chronological order we find that in 1865 the Penn. sylvania R. R. Co. made efforts to secure flange plates of American steel for its locomotive boilers. The steel then used was crucible steel, made by a Pittsburgh firm. So satisfactory were the results that in 1866 this company built no less than eleven locomotive fire boxes of the same material. In June, 1866, was built the first locomotive boiler entirely of domestic steel, crucible made and of high cost. At this time the Bessemer process was but just established in the United States, and the open-hearth process not yet introduced. Despite the evident superiority of the new material, it was not until 1873 that steel wholly superceded iron for boiler purposes, even in this company.

In the navy a high grade of steel was used for steam launch boilers in 1872, but it was not until the spring of 1878 that the first large marine boiler of steel was placed on board the fish commission steamer "Lookout," and the "Nipsic" was the first American man-ofwar to be thus equipped, in the fall of the same year.

For structural purposes crucible steel, hardened by an alloy of chromium, was employed in the Eads St. Louis bridge in 1869. Though successful in all respects, the experiment has not been repeated.

Practically, mild steel for bridge building dates from 1879, when Bessemer plates and girders were incorporated in the approaches to the East River bridge. From this date also open-hearth steels entered largely into bridge structures. None of the bridge steels of that time would now be called mild steel, as the T. S. was from 70,000 to 80,000 lbs. per square inch, and the elongation only 20 per cent in 8 inches. The total amount used was small, as the aggregate of all classes, crucible, open hearth, and Bessemer, was but 18,000 tons in the fifteen years from 1869 to 1884.

In ship building we did nothing whatever prior to 1879. In that year three vessels of an aggregate tonnage of 246 tons were built for river navigation. Up to 1883 five more, including lighters, were constructed. The total tonnage to this date was less than 500 tons. All of these vessels were steel plated only. Practically, then, steel ship building was an unknown art, the material untried, and the workmen unskilled, when the frame of the "Dolphin" was laid down in 1883.

Such was the status of the steel industries as regards structural material when Congress authorized the constructien of our four first ships of mild steel of domestic manufacture. The courage and foresight of the Advisory Board of Naval Officers, upon whose recommendation Congress acted, are entitled to recognition. Iron ship building was already an established industry, and its results certain. As to steel (this was in 1882), there were difficulties in production, as yet imperfectly understood, and but partly overcome. There was the still more serious objection of the utter lack of workmen skilled in the manipulation and assembling. The compelling reasons leading to the Board's decision are here given :

cost.

1. Great saving in weight of hull, compensating for difference in

2. Increased strength in hull.

3. Increasing success attending construction of steel hulls abroad. 4. The certainty that steel in the near future is to supplant iron in ship construction. (A prophesy virtually fulfilled.)

5. The impetus that such a step taken by the government would give to the general development of steel industries in this country.

6. The necessity that the new ships shall in all respects equal, if not excel, ships of other navies, class for class; and,

Finally, that for the reputation and the material advantage of the United States, it is a prime necessity to take a bold and decided step to win back from Europe our former prestige as the best ship builders in the world.

From these seven patriotic, courageous, and far-seeing conclusions the navy has never receded. The success of the new vessels has evidenced their wisdom, and the merchant marine has been quick to follow the initiative.

Quality and cost were undetermined factors. The specifications were high, and the requirements rigorous. Replying to circular letters, the manufacturers expressed confidence as to the quality of their steels, but doubted their ability to supply the special shapes required. It is a somewhat caustic commentary on the actual capabilities of the time that the quality failed, though sections were up to standard.

At this time the largest ingots were of five tons, the heaviest plates but 1", weighing about three tons each. Thirty feet long I beams of 12" section almost stalled the heaviest rolls. At present the Bethlehem Iron Co., of Bethlehem, Penn., are casting ingots of 100 tons weight, and are producing curved plates 17' x 6' x 17′′ thick, and 16' x 9' x 12" thick, weighing 36 tons each, finished. There are at least six other firms who are now prepared to furnish plates up to four inches in thickness.

The specifications which were drawn up in June, 1883, called for mild steel for hulls with T. S. of at least 60,000 lbs. per square inch, and elongation of not less than 23 per cent in eight inches. Boiler plates specified not less than 57,000 lbs. nor more than 63,000 lbs., with a ductility of at least 25 per cent.

Under these specifications contracts were entered into for the construction of the A, B, C, D ships in July, 1883. Three of these ships, the "Atlanta" and "Boston," of 3,000 tons displacement each, and the " Chicago," of 4,500 tons, have recently visited this port. Since then they have weathered storms of unusual winter severity in crossing the Atlantic, and are now in Europe. The D, the Dolphin, a dispatch boat of 1,500 tons, has recently refitted in New York, after

a voyage of over 45,000 miles around the world. That these ships have shown themselves equal in construction and material to the strains and service for which they were designed has been abundantly proved. During the construction of these vessels a determined effort was made to break down the system of naval tests and inspection. The reasons assigned were impracticability and expense. Delays were not only exasperatingly frequent, but failures also were many. The specification as to ductility was lowered to 21 per cent, and some slight modifications made as to methods. The system then established is the foundation of our present inspection. Each new vessel is built of better material than her predecessor, and the requirements keep in advance of the material. In 1886 the Steel Board succeeded the Advisory Board, and has for its function the inspection of all steel material for hulls and machinery.

Attention was called to tables on the board which showed the increasing severity of the specifications, and the changes due to experi

ence.

In hull plates and shapes we find the tensility constant at 60,000 lbs., but the additional safeguards of chemical conditions and surface inspection, aided by additional tests, serve to show the good or bad quality of the material better than either T. S. or elongation.

Up to 1876 steel was generally accepted on the maker's guarantee. From that time, however, testing of steel, particularly boiler steel, came in. The features of the Pennsylvania R. R. Co.'s inspection, which are quoted as being the most thorough before the navy inspection began, were:

1. Careful examination of every sheet for mechanical defects.

2. Tensile test; 55,000 lbs. per square inch, ultimate strength. Elongation; 30 per cent in 2 inches. Both of these were averages. The limits were: tensile, minimum 50,000 lbs. ; maximum 65,000 lbs. ; elongation, minimum 25 per cent.

3. Rejection of sheets developing defects in working.

4. Coupon tests for each sheet.

No conditions were imposed on impurities beyond those which the manufacturer knew would affect surfaces, and cold or hot shortening.

The inspection of steel for naval purposes contemplates that the inspector should thoroughly familiarize himself with the composition of the furnace charges. As the variations in the pig and mill irons,