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Lake Freight Matters. Although the aggregate output of iron ore from Lake Supe- rior mines for the full season will not drop to 4,000,000 tons, as some predictions would indicate, it will certainly not be much, if any, above 5,000,000 tons, against a little more than 9,000,000 last year. Statements for the month just closing will very prob- ably show a reduction for the month equal to about 50 per cent. of the entire reduction for the season to Aug. 1. Among all in- terests, something of an improvement in freights for the balance of the season is expected, but it is very slow in coming, and al- though there has been a fair movement of grain out of Chicago, vessel owners are gradually inclining to the opinion that the wheat in store there is held by the speculators, aud will not be moved forsome time tocome. Several times during the past ten days, since money matters have eased upa little, there have been signs of more activity in both coal and grain, but the amount of tonnage offering, even with the large number of vessels laid up, is still in excess of the demand. A general improvement in freights would prompt an early advance of 5 or ro cents in the very low ore freights, but there is no hope of ore freights leading the general market, excepting in the event of additional ore sales, which seems highly improbable under the present condi- tion of the iron market. It is generally admitted that coal dealers of Chicago and northwestern points are very much be- hind their requirements in receipts of coal by lake, although their docks are crowded in many cases now so that they can not store more coal. '"'At this time a year ago," said a Chicago dealer who was in Cleveland recently, "I had cleared my coal sheds three times, through shipments to small dealers, and was beginning on the storage of another supply for the winter. This year we have not only failed to clear the sheds at all, but have shipped only a small number of cars, and we are loaded up with coal received by lake early in the season. Very high prices are certain to prevail all through the west for coal during the fall and winter." Ship Building and Engineering on the Great Lakes. Of all the papers presented to the Engineering Congress, held in connection with the World's Columbian Exposition, that of Walter G. Miller, superintending engineer of the Globe Iron Works Company, Cleveland, was most exhaustive, and showed most labor and expense in its preparation. This is not said on account of any local pride on the part of the REviEw, as the paper was most highly complimented by Commodore Melville and Past Assistant Engineer McFarland, the chief officers of the branch of the congress devoted to marine and naval engineering and naval architecture, 'The paper is accompanied by about thirty engravings of hulls and machinery, made from plans of different types of lake vessels turned out, within the past ten years, from several lake shipyards, and in this respect will, in itself, make the report of the proceedings of the congress, to be published shortly, a most valuable book of reference for every- body interested in lake shipping. During two or three years past, the REvrew has succeeded, with considerable difficulty, in placing before its readers sectional drawings of some of the modern lake vessels. In one paper Mr. Miller now presents thirty or more such drawings, not only of vessels built by the Globe company but also of the passenger steamers and car fer- ries constructed by the Detroit Dry Dock Company and the whalebacks from the yard of the American Steel Barge Company. Mr. Miller takes up the subject of ship building and engin- eering on the lakes from 1881, a period when the adoption of iron asaship building material, and the introduction of compound engines for the propelling power, began to be considered. The paper deals quite extensively in statistics of lake commerce from authentic sources, and then to facilitate a description of lake steamers and their machinery, which is the most important part of the work, the vessels are divided into four principal classes, MARINE REVIEW. Pe designated as follows: First and most important, the ore, grain and coal carriers; second, package freight, coal and grain; third, lumber and coal; fourth, passengers and miscellaneous freight. A general description of these different kinds of vessels follows, and then the best practice of ship and engine builders on the lakes is shown in detailed descriptions of the most important types, accompanied by drawings in plan and section. Of the modern ore and grain carrier there are illustrations showing mid- ships and longitudinal sections, spar deck vlan, side elevation of ' vessel and cross sections through engine and boilerspaces. The drawings of other types of ships and engines are equally com- plete, and among the boats specially described are the Detroit and Cleveland Steam Navigation Company's paddle steamers, a whaleback steamer 265 feet in length, one of the double screw car ferries running in the Straits of Mackinaw, the twin-screw passenger steamer Virginia and one of the big twin-screw ex- press steamers building in Cleveland for the Northern Steamship Company. Why Oil has an Influence on Waves. A great deal has been written about the influence of oil on waves at sea, and of the practically useful action of oil in many well recorded cases there is abundant testimony, but little has been heard of the reason for the results so obtained. W. J. Millar, secretary of the institution of engineers and ship builders in Scotland, treats of this side of the subject in a paper submitted to the recent Engineering Congress at Chicago. He says: "Rrom experiments made in shallow, broken water on the coast, where the wind and tide conflicted, it would seem that little or no advantage is apparent in such circumstances; that is to say, the wave-motion being disturbed and under forces not wholly those of wind action, the oily film becomes broken up. In deep water, however, where the waves may be considered as wholly formed by the wind, their torms are more regular, and it is in such circumstances that the recorded examples show to best effect. 'hese facts in themselves point in some measure to the real action of the oil. According to some theories the oil acts as it does when applied to bearings in machinery, and thus the © wind glides more readily over the oiled surface than it does over the water surface. It is difficult to see, however, how the fric- tional resistance between air and oil should be less than between air and water, as the oil is a less mobile fluid than the water. Again, when we consider the surface tension of fluids, and can often observe their restraining action on ascending airbubbles or small floating objects in glasses of water, we might suppose that by the addition of the film of oil sufficient resistance was offered to the uprise of the upper part of the wave, and thus the tendency to break would be restrained. 'The author, both from experi- mental results and other data, has come to the conclusion that the action of the film of oil is one of separation. Thus it seems "to him that when we consider the tendency of air to become saturated with watery vapor due to evaporation, and of water to retain air by absorption, we may readily conceive that the im- pact of air on a watery surface will tend to cause a commingling at the surface of air and water, which will thus offer sufficient resistance to the motion of the wind to throw the water and | mixture into an undulatory movement, and therefore, when this forward movement has exceeded the speed due to the periodic motion in the wave itself, the upper part in falling forward, due to the push of air from behind, shows a foaming rush of broken water; that is, the air incorporated with the water and the water itself. If this be admitted, it is easy to see how a film of oil spread over the surface of the water may effectually prevent the formation of broken water, as the air and water will be kept separate, the tendency to mutual absorption at the surface will be checked, and the wind will therefore pass along the oily sur- face with reduced power of wave-making," -