gulf to the lakes. We might then in comparative safety and freedom from anxiety, set about those further means of defense which the lake region so much needs. Now, we are almost defenseless. Then we could defend our harbors and cities, or taking the offensive, threaten those of the enemy, or fight him on fair terms. For the accomplishment of these desirable ends our fleet of river gunboats now in use is entirely unsuited, as they could not live an hour in rough weather on the lakes. Can there vessels be built which can pass through the proposed canal, and yet be capable of doing good service on the lakes? Upon the answer to this question of course will depend the utility of the proposed work in regard to the defense of the lakes. Not only can vessels be built which will answer these conditions, but a fleet of them already exists. Acting Rear Admiral D. D. PORTER, commanding Mississippi Squadron, in answer to my inquiries on this subject says: "That a canal and locks of the dimensions contemplated will pass nearly every large, light gunboat we have in the navy, or that would b› built for lake or sea service. Any vessel drawing eight feet can be lightened to six and-a-half by taking out her battery, coal, and stores." He then names several boats of both the river and sea going class which could pass through the canal, adding, "and some fifty vessels of their class." This, I take it, is satisfactory on this point, about which some good friends of the project had entertained doubts. It may be observed also, in reference to the present river gunboats, that although they are unable to encounter successfully the waves of the great lakes, it will yet be very useful to be able to take them for repairs, up to the workshops at Chicago, and other towns along the line. It is difficult to imagine a stronger case of military utility, not to say necessity, than is presented in this relation of the proposed communication to the defense of the lakes. Argument can hardly add to the force of the simple statement of the facts. Not only would any fleet of gunboats when built be doubled in value, but the vast resources of the lake country in oak and fine timber and iron be available for further increasing the number. Besides the lessons which the ship builders of the lakes have learned under the necessity of adapting their vessels to the comparatively shallow harbors of these waters, and uniting carrying capacity with light draft, will be found of service in this connection. Their skill when called into exercise by the government, will combine the timber of the shores of Lakes Michigan, Huron, and Erie, and the tough iron of Lake Superior, into vessels able to carry the flag of the nation with honor to the torrid regions of the Gulf. Look a moment also at the great facilities which this route will offer for the transportation of troops, supplies, and munitions of war when needed. The saving of water, over railroad transportation, and of large boats over small ones, is well known. It has been often exhibited in the most striking manner during the present war. A few words seem to be demanded on the more general view of the subject. Its bearings upon the commercial, manufacturing, and agricultural industry of the country. The subject is so vast that I almost hesitate to say anything about it in the parting way in which other pressing duties will oblige me to do. The great lakes and the Mississippi river are among the grandest features of the geography of the globe. Their names are at once suggestive of commercial and agricultural wealth and national greatness. No such sys-. tem of internal navigation exists elsewhere in the world. The most careful and accurate statements of their present uses for commercial purposes are truly wonderful, while the magnificent future to which enlightened enterprise may lead, tasks the strongest imagination. The Mississippi system of navigable waters is variously estimated at from 10,000 to 20,000 miles. Its numerous ramifications penetrate a country of unrivalled fertility and in many parts abounding in the useful metals. On the lakes we have a coast of 3,500 miles. Their commerce is estimated at the value of $400,000,000, in articles of prime necessity, to the inhabitants of Eastern States and to our foreign commerce." That of the Mississippi in peaceful times is supposed to equal this. It is the union of these two mighty systems that we contemplate in the proposed improvement. For this purpose no other route exists comparable to the line now proposed, in the economy of cost of the improvement, or in general utility. It is one of nature's highways, one of the lines which she marks out for the guidance of the great emigrant movements of the race, and by which topography foretells the march of empire. The aboriginal savage traveled by instinct, and now educated intelligence can find no better place for completing and uniting lines of travel and traffic embracing half a continent. From what has been we may foretell what will be. When the present disorder shall have passed away, the interchange of products between the Northern and Southern States will be resumed. The cotton, sugar, and tobacco of the South will seek its market throughout the Northern States and Canadas, and in return the North will send its wheat, corn, pork, beef, and the various articles of manufacture, which it can so readily provide. This great commerce will gravitate to the cheapest channels. "Look a moment at the capacity of the canal and river improved as proposed," says Mr. GOODING in a recent letter. It is believed that a boat or barge, built something like our canal boats but cheaper, would usually carry the freight instead of the steamer itself. But suppose our present canal boats be used; twelve of them carrying over 70,000 bushels of grain, with less than five feet draft of water, could be locked through one of our contemplated locks at one lockage, occupying perhaps fifteen or twenty minutes. A powerful steam-tug, such as is used for towing ships from the mouth of the Mississippi to New Orleans, would easily tow such a fleet of boats. It will therefore be apparent that were much less than one-half the old prices paid for freight it would pay enormously with this improved navigation." gives certainly a very striking view of the facilities for transportation which the improvement will offer. This Consider, too, that these facilities will be constant through the seasons of navigation, not fluctuating, as is usual now, between flood and drought. The present season has been one of unusually good navigation in the Illinois river. The result is remarkable. With the report of the House of Representatives, heretofore referred to, was submitted an estimate of tolls, etc., for the five years proposed to be occupied in the construction of the canal, which can be so carried on as not to interfere with the navigation. The tolls for the first year are put down as likely to be the same as for the year 1861, viz: $218,000, and for the second at $230,000. I am informed that the tolls received up to a recent period, during the present season, exceeded those of the last year up to the same time by $40,000, and the receipts for the full season of navigation will not be less than $260,000, and would have been from 25 to 30 per cent greater if there had been canal boats to do the business The uncertainty of navigation in past years, owing to the liability of low water in the Illinois river, has discouraged boat-building, and the supply of boats is unequal to the demand. These facts point to the most favorable results to follow, upon making the navigation constant throughout the season, along the whole line from the Mississippi to the lake, to say nothing of the great increase which must inevitably follow the completion of the enlargement, affording so much greater capacity and economy. Cheaper transportation attracts a larger amount of freight and increases the revenue even at reduced rates of toll, as is shown by the Erie Canal. The two parts of the work are necessarily dependent upon each other, or rather the canal enlargement and the river improvement make but one work. It will not be worth while to make the one without the other. It is stated that the tolls on the Erie Canal for 1861 were $3,800,000. It cost $40,000,000, and is 352 miles long. This proposed improvement is 316 miles long, of greater capacity than the Erie, and can be completed for $13,346,824. From a fair comparison of the two works, what may be expected of this? It will draw trade from down the Mississippi, from the Rocky Mountains, by way of the Missouri and the Yellowstone. The whole of the western half of the Mississippi system will be naturally tributary to it. While in turn it will pour through its capacious channel the merchandise and manufactures of the East. If, then, the present contracted canal, ninety-six miles long, and without facilities for doing all the business offered in a season of good navigation yields $260,000, may we not firmly expect that when the whole line of 316 miles is opened on the proposed scale, reducing the cost of transportation in proportion, it may yield five time that amount? Or, if the work should cost $13,500,000, the interest on its cost would be $810,000. Taking the tolls to be derived from the enlarged work, shortly after completion, at only four times what they are for the present year, the amount would be $1,040,000, which would pay the interest and loan$230,000 per annum, for repairs and superintendence, etc. Surely this may be considered altogether within bounds, when we look at the growth of the country now going on, and the additional stimulus which such a work would give. The country which will seek this route for its commerce has hardly commenced its agricultural development; hardly one acre in ten is under cultivation, and in large portions not one in a hundred. The want of facilities for transporting produce now represses the growth of this region, by tending to reduce the price of its products below a remunerative point. The East is directly interested in this matter. Any considerable reduction in the cost of transportation here would cheapen the food of every operative in the Eastern manufactories, and tend to draw from Europe the skilled laborers we so much need. Another point is worth mentioning-the effect of such a work in increasing the assessable value of property in the region more directly affected by it. Of course nothing very definite can be arrived at in this direction. Analogy may help us as to some approximation to the amount. One of the projectors of the Erie Canal estimated its effect in this way, in five years, at full $400,000,000; and the differences between the two cases are all in favor of that under consideration. In the vast region communi cating almost immediately with this line, nearly the whole of the land is capable of profitable cultivation, and only waits increased means of transportation to be brought rapidly into use. But is the work national, so that Congress may rightfully execute it? A glance at the map will furnish a sufficient answer. Let the eye follow up the Mississippi, and crossing over to the lakes, dwell a moment upon the line of this work. How little labor and expense will suffice to effect a union between these two great systems of water? As the observer looks and thinks, the greatness of the idea will more and more open upon him. Its military and commercial bearings will develop into vaster proportions, till he will see that nowhere is there a work to compare with it in importance, except perhaps the projected canals across the Isthmuses of Darien and Suez. All of which is most respectfully submitted by your obedient servant, Estimate for a ship and steamboat canal from Lake Michigan to the Illinois river, and the improvement of the Illinois river to the Mississippi river; the canal to be 160 feet wide on the bottom, sides protected with stone walls 10 feet high; the canal and river locks to be 350 feet long and 70 feet wide, with depth of water sufficient to pass steamboats and vessels drawing six feet of water; the canal to be supplied with water from Lake Michigan. Chicago to Lockport, 29 miles: The estimated cost of earth and rock excavation on the summit level from Chicago to Lockport, with walls on both sides 10 feet through the earth, is.... Lockport to La Salle, 67 miles: ...$7,092,700 The estimated cost of canal to Lake Joliet, and short canals at sixteen locks, walled on both sides; also six stone dams, 600 feet long, eleven canal and five river locks, each 350 feet long and 70 feet wide-making 138 feet of lockage between Lockport and La Salle-is... La Salle to the Mississippi river, 220 miles : The cost of seven tree and crib dams, 900 feet long, the cribs to be filled with stone and stone abutments; also seven stone locks 350 feet long and 70 feet wide, with entrances protected, and insuring a depth of water on all bars to pass the largest steamboats and vessels drawing six feet, will be.... Add for bridges, right of way, engineering, contingencies, etc.. 4,031,092 1,045,000 578,032 Total. $13,346,824 THE MARINER'S COMPASS-IRON SHIPS. THE Jury at the International Exhibition on Ship Equipments, etc., in speaking of the mariner's compass, observe with satisfaction the progress generally made in the construction of this invaluable instrument. This is progress, they very properly remark, in the right direction; for, with the increasing use of iron in ship-building and fittings an efficient compass is imperative, and thorough efficiency cannot be secured without the greatest care in details and delicacy of manipulation. In 1851 the laws and general principles affecting the compass in iron ships were professionally unknown. They had seriously engaged the attention of a few leading men of science, and so far back as 1839 the present Astronomer Royal of England had made an extended series of experiments by the desire of the Lords Commissioners of the Admiralty in the iron merchant ship "Rainbow." The resulting abstruse investigations did not receive then the attention they merited, though a tentative mode of adjusting the compass published in 1840, by Mr. AIRY, became the basis of a system of compensation since generally adopted in the mercantile marine. The rapid increase of iron built ships subsequent to 1851, and the consequent appreciation of compass disturbances produced numerous plans; some for detecting the deviations without the aid of astronomical or other well known observations, others for correcting the deviations by peculiar arrangements of magnets, and even appliances for isolating the compass from the effects of local attraction appeared; many of these plans resulting from an imperfect knowledge of the laws and mode of action of magnetism were undoubted failures. The melancholy loss of the iron emigrant ship "Taylour," with a great number of her crew and passengers, on the east coast of Ireland, in the early part of 1854, was traced in the main on the official inquiry to the changes of the ship's magnetism, or the imperfect action of the compasses which had been compensated at Liverpool a few days previously to the ship sailing from that port. Public opinion, which was much divided on the subject, eventually invoked the aid of science. A special discussion took place at the British Association at Liverpool in 1854, and ultimately a committee composed of practical and scientific men, interested in the question, was formed at Liverpool for the purpose of collecting informa tion and making the necessary experiments. Three reports of this com mittee, the last dated February, 1861, have been presented to the Board of Trade, this department of government having liberally assisted the inquiry throughout. To this source and to the investigations of the Astronomer Royal and ARCHIBALD SMITH, Esq., F.R S., with the researches in the same field by other well known names, among whom we may worthily select the president of the Royal Society, General SABINE, we may have every confidence that a secure foundation of the theory and practice of compass management in iron ships is laid, which alone requires the general spread of education to render familiar to the intelligent seamen. |