MARINE REVIEW. II [Continued from page 7.] creased, and thus tend to prevent any beneficial results accruing from the regulating works. It would therefore appear that in order to be able to secure any substantial benefit from the regulating works at the foot of Lake Superior, the Jevel of Lake Erie must first be regulated by a dam at the head of Niagara River. It is a well known fact in hydraulics that where water flows over the crest of a dam or weir, any slight variation of the depth on thecrest of such weir will very materially modify the volume of discharge passing over. For instance, if the top of such a weir is two feet below the general level of the water surface of a regulated lake, anda rise of three inches froma heavy rain should occur, the volume of discharge over the weir would be increased 20 per cent.; or, if such were the conditions on the proposed dam for regulating the level of Lak2 Erie at a time when the discharge was 250,000 cubic feet per second, corresponding to that of the present mean stage, the increase would be 50,000 cubic feet per second; and since the in- crement for one foot change of level at such stage is probably not far from 33,000 cubic feet per second, tie change of three inches above the regula- ting dam would correspond to that of 1.5 feet under the present conditions of the lake outlet. A sudden rise of three inches under the existing conditions would not increase the outflow to exceed 10,000 cubic feet per second, from which it is evident that a properly constructed regulating dam at the foot of the lake would greatly increase the discharge of Niagara River for small rises of the lake level, and consequently lengthen the period of maximum dis- charge and proportionately diminish its volume of flow per second at high stage. That such a dam can be constructed, there is no question; but what its dimensions should be, and what it would cost to construct it can not be stated until the discharge of Niagara River is accurately known. Since the difference in the levels of the water surfaces of Lake Huron and Lake Erie seldom varies more than six inches from the mean slope of tLe connecting waterway, it is evident that if the level of Lake Erie be so1egu- lated as to vary but little from its present high water stage, the annual fluctuations of water surfaces of Lakes Huron and Michigan will be de- creased so much as to produce the necessary change in slope in the St. Clair and Det:oit rivers corresponcing to the variation in discharge--a probable extreme fluctuation of less than 1.5 feet. This result will directly effect the levels of the St. Mary's River below the falls, and will unquestionably add at least two feet to the low water depths of that river. The laws governing the flow of water over the crests of dams are definitely known, and if the level of Lake Erie be determined, near which it will be safe to regulate the water surface without damage to property, the problem of regulation becomes simply what length must be given to the dam, such that a fluctuation of six inches on the crest will correspond to a variation in overflow equal to the maximum annual variation in the discharge of Niagara River. The solution of this problem rcquires an accurate knowledge of the outflow through the Niagara River for all stages of the lake level--data, which at present are so uncertain that the computed outflow by different engineers differs by amounts which would make a large river. If this project is worthy of official investigation, the first and essential thing necessary is that the physical facts in regard to the water levels and outflow of the lakes be accurately determined. Aside from the important question under consideration, this information is badly needed to settle ex- isting disputes as to what effect certain canal and harbor improvements are likely to have on the channel depths of the lake waterways. With sucha regulating dam in place, the annual discharge of the Niagara will be the same as under the present conditions, but at the begin- ning of a rise of the lake surface, the dam will add greatly to the outflow and correspondingly reduce the maximum discharge for the high water period. It is the opinion of the writer that such a dam will be ample to regulate the levels of Lakes Erie, Huron and Michigan, but in case the future development of the lake commerce makes still further improvement neces- sary, a regulating dam at the foot of Lake Superior would place the levels of the entire upper lake waterway system under perfect control. Since the water surface of Lake Erie, when properly regulated will not have an annual fluctuation of over six inches, and since the present high water plane of lake levels is 2.3 feet above that of the mean stage, if the regulated plane for mean discharge he fixed at 1.5 feet above the present mean level, the high water stage of the regulated surface would never ex- ceed the present high water plane. And as it is fair to presume that all structures have been built with due regard to safety under existing condi- tions, no great damage could possibly arise from the improvemen.. Since the fluctuation of the regular water surface will be small, all future structures can be built at heights best adapted for economical handling of freight, and have the great advantage of being in such state at all seasons of the year, a condition of affairs all shippers will appreciate. In a letter published in the Marine Review of September 7, 1893, a distinguished engineer officer says in regard to the effect of such a dam on - the level of Lake Ontario: "The result could only be produced by im- peding the discharge of Lake Erie, and as the level of ake Ontario de- pends on this discharge, it is evident that the level of the latter, as well as of the upper St. Lawrence River, would fall until the discharge over the proposed dam was restored to the present volume. Then the surface of Lake O.tario would begin to rise, and continue rising until the present level was attained. The length of time required to pass through this cycle is inderminate, but it can be assumed with reasonable assurance that the period would be so long that the people of the United States and Canada interested in the navigation of Lake Ontario, St. Lawrence River and St. Lawrence canals, would so strongly object as to prevent the con- struction of a dam atthe outlet of Lake Erie." This is a strong criticism from an engineer of recognized authority on such matte:s, and unless it can be squarely met with legitimate reasons to the contrary, might be sufficient to prevent the enterprise being under- taken. The area of the water surface of Lake Erie is 9,960 square miles, and of the entire lake basin tributary to the lake 230,000 square miles, or ap- proximately 23 times the lake surface. Since about 50 per cent. of the rainfall on the basin is discharged through the Niagara River, it is evi- dent that a variation of three inches in the rainfall on the lake basin would be equivalent to a volume of water due to a three-foot change in the level of Lake Erie. ae Since the variation in the rainfall on the lake watershed is over 18 inches, and produces no disastrous effects on the levels of Lake Ontario, it is cifficult to understand why only one-sixth of this volume, if held back by a regulating dam, should produce any noticeable effect whatever. The work of constructing such a dam would extend over a period of at least two years, which would make the effect only one-half that men- tioned above, and the criticism can therefore be dropped as a purely theo- retical one. Cheap transportation depends largely on being able to carry large quantities of freight in full loads, long distances, without change and at rapid speed. To dothis, ships must be constructed with due regard to the depths of the waterways which they are to traverse, and since the capacity of a waterway within ordinary limits varies as the cube of the depth, the draught of vessel must be such as to utilize as great a depth as possi- ble, without causing speed to be retarded by too close proximity of keel to the bottom. For waterways of constant depth, the most economical draught and tonnage for a vessel is easily determined, but where the water levels have fluctuations of several feet, the solution is very complicated and unsatis- factory. On the lakes, freight vessels have generally been constructed for the deepest summer depth to be expected in the waterways, with the result that during low stage of water only partial loads can be carried, which, with de- tentions from groundings, greatly reduces the profits of the shipping business. ; It would therefore seem almost self-evident that any system of improve- ment of our harbors and waterways, having for a basis the regulation of the water levels, must have a very beneficial effect in cheapening vessel construction and transportation rates. It is a well established fact that the tendency of export products is to follow the same lines of transportation used for supplying the necessities of home consumption. The surplus products of the Northwest will therefore very likely con- tinue to be transported over the water and railroad routes through our eastern cities. This convention has been convened to devise ways and means to ren- der the cost of such transportation a minimum by setting the proper ma- chinery in motion to have a waterway of a fixed depth of over 21 feet con- structed from the lakes to tide water; but unless some radical change is made in the methods of improving the waterways of the lakes, vessels loaded for the full navigable depth of such ship canal will be badly handi- capped when chartered for ports beyond the western terminus of the canal during the low water season on the lakes. It has already been shown that the cost of increasing the harbor channels and lake waterways has been nearly $5,000,000 for each foot in depth secured in both, and that un- der the present system of improvement, such results haye not been per- manent. It would therefore appear very desirable that an investigation be made of the feasibility of increasing and rendering nearly constant the depth of navigable channels of the lakes, by regulating the lake levels, a d that such investigation should be made by the International Commis- sion to be appointed, and I understand already provided for, to report on the character, route, and cost of a ship canal from the great lakes to the sea, For Sale Cheap . FOUR HARBOR ruams ALL WITH ENGINES 18x 20, AND IN GOOD CONDITION. HIGGIE & SHAW, Vessel Agents, . No. 1 Franklin Street, CHICAGO, ILL. Jeffery's Marine Glue For Paying Seams of Decks and other purposes. L. W. FERDINAND & CO., Boston, Mass. TN ea S68. 2 ee ee ee ee ees - Send for Circular.