At a meeting of the Institution of Naval Architects, recently held in London, Mr. Scott Russell delivered a very interesting discourse on Railway Communication across Lakes, Straits, and Arms of the Sea. He said that, as they had very olten to cross the English Channel, it was a great act of international cruelty to keep up such a wretched communication between Calais and Dover, as the great British nation and the great French nation now combined to keep up. It was now more than three years since that eminent engineer, Mr. Fowler, became engineer to an association for putting a railway between Dover and Calais; and he (Mr. Scott Russell) was the naval architect for the steamships that were to make this communication. All the Surveys had been made, all the plans had been prepared, and all the preliminary legal steps had been taken for bringing the scheme before the Houses of Parliament. But it was an unlucky period. Rail-Way companies were quarreling with and ruining each other, and a scheme which, merely interested the traveling public could not at that time command successful attention in the legislature or in the community. He might state that the plans had been fully matured. They had provided plans of the works by which railway trains s-ould descend the pier at Dover, go into the vessel, cross ffver to Calais, and go from Calais right on to Paris, and nee tana; so-that a passenger from London would, by a night trsii, take his seat or his bed in a railway carriage at London Bridge, and would open his eyes in the railway station at Paris, unconscious that he had crossed over the sea. That was a conclusion which he dared say people would gladly see realized; -but he could not hold out any prospect of its being speedily realized, because we were such a patient people that it was likely for the next ten or twenty years we should be content to make passage as we had always done. Curiously enough, about a year after this he was invited to look at the inland sea which separates Switzerland from Germany. What the Germans call the Bodensee, and what we call the Lake of Constance, was a great inland fresh-water sea, sixty or seventy miles long, and eight to twelve miles broad. The railways of Germany came close down to the Gorman side of the lake, and the railways of Switzerland came down to the opposite side of the lake : and there the communication between the two countries was as completely interrupted as our communication with the Continent was blocked by the Straits of Dover. The reason why they did not carry the railway round the lake was obvious: the lake ran up into the precipitous Alps, and was continued over to the Italian side, so that no railway could find its way through. The Alps, with the Bodensee, formed an impassable barrier between Switzerland and Germany on one hand, and between Germany, and the middle and south of France on the other. This was an enormous evil. A large proportion of the supply of France with corn came last year from Hungary by railway and across the sea. Every sack of cofnhad to be unladen from the wagons, to be shipped, to be taken across, to he unshipped, to be reladen on the wagons. The cost of this transhipment, independent of the delay and blocking of the way, was greater than the carriage of the corn for the hundred miles by railway. It so happened that he had built the first fast vessel on that lake twenty years ago. It was a good, honest ship, and, as good, honest work always brought its own reward, he was called upon to solve the much more difficult problem of effecting communication between the railways on the two sides of the lake. The problem they set him was, What we want is that you will make uS the nearest thing you can to a railway, in order that we may let our trains, with their locomotive engines and everything, go across the lake as if it were a railway. Well, that was not difficult to do. The only difficulty was to do it well, cheaply, and in such a manner as to suit the peculiar circumstances of the case. The peculiar circumstances of the case were these : That at the entrance of the harbors the channels v.rrro shallow, not more than six feet deep. That was a difficulty. The next difficulty was that the harbors were so small that there was barely room for such a vessel as would carry a train to get into the harbor and turn round. More than that, the entrances to the harbor were extremely narrow, so that in all these points, the case was a far more difficult one than the case between Dover and Calais. It might be said that he had not the great Atlantic waves to deal with. That was true; but there was something else— there was the terrific mountain hurricane, that came down so suddenly that it raised a nasty, short, sharp sea, and he need not tell them that a nasty, short, sharp sea, with a tremendous wind, was very often more troublesome to deal with, especially in shallow water, than a gentle swell would be. Another difficulty was a change of level of water, amounting to twelve feet from one extreme to the other. It was true this level did not change every day as at Dover, but it did change periodically, and therefore it was necessary to have a similar provision. Having stated the peculiar circumstances of the case, he would shortly describe the manner in which those circumstances were met, and he would also state the results, because it would show that the difficulties between Dover and Calais could be met in a similar way. If he was asked the comparative difficulty of the two problems, he could not say that one problem was more difficult than the other. He had solved the Dover and Calais problem three years ago in plans, but he found that lie had an enormous deal to learn and contrive before he could solve this particular problem in Switzerland. He proceeded to show how this problem was solved. In the first place, he said to hJHjFelf, If they want me to continue the railway across the sea, I had better take a slice of the railway station, put a train and an engine into it, and send it over to the other side, and a train will then go on. He therefore took a section of a railway station 23 feet wide, and put upon that two lines of rail on one side and two lines of rail on the other side, leaving these two lines of rail to receive two railway trains. He had then to let in a locomotive engine, and so he had to make the roof of his railway station as high as a railway bridge, or a little higher than the top of the engine chimney. The next thing was to float this bit of a railway station. Of course that was very easily done. He had only to put a construction below it in the nature of a ship, and, as there was only 6 feet of water, he had to take care that his vessel only drew 6 feet of water. The midships was 4 feet more out of the water when laden, so that below the railway platform there was a depth of 10 feet only. But this was not enough. Having got to propel the vessel, he had to place an engine room and boiler on each side, each 9 feet wide, making, with the 22 feet of railway, a total width of 40 feet. The boat had next to be fitted with puddles, which occupy a space of 10 feet on each side. So thvS, altogether, the structure was 60 feet beam. And when he stated that the harbors were from 80 feet to 100 feet wide at the entrance, and that he had to enter these harbors in hurricanes in shallow water, at a low velocity, with scarcely any steerage power, it would be seen that the task was not very easy. Perhaps he ought to say a word about the engines. At the beginning there were a few particulars that bothered him. He wanted to get the paddle-shaft all through, but he could not. If he put it below it was too low; if he put it above it was too high; so he gave it up altogether, and simply put upon the shaft of each paddle wheel a couple of oscillating engines—one before the axle and one behind the axle. So he had a pair of engines to each wheel, perfectly independent of one another. A nautical friend would say to him, You will get into precious difficulties with them. He knew he should. He knew very well that in a heavy wind, when one paddle wheel was deeperthan the other, one engine would be flying away, and the other would be workingvery slowly. To counteract that he took a little indicator from the right engine room into the left engine room, and anotl er indicator from the left engine room into the right engine r om; and he made these indicators go round in the face of the engineer, so that he could not help looking at them when he was starting, or reversing, or moderating his engine. By this means engineer A was always looking at indicator B, and engineer B was always looking at indicator A; and in three days they had acquired such skill in handling the engines that engine A and engine B never advanced half a turn upon each other. These were the difficulties he. had on the cross secWois 306 There were also difficulties on the longitudinal section. On thef line of rails he had to put his wagons, eight wagons on each line. German wagon were desperately long; but, having two lines of rails, he was enabled to carry nineteen wagons in all. The incovenience which he was obliged to submit to he had already mentioned, that arising from the shal-lowness of the water. He could not have deeper water than six feet, and he could not raise his vessel more than four feet above the water on account of the hight of the piers in the harbors. Therefore he was limited to ten feet deep. But he need not say that ten feet deep was much too shall ow for a good strong vessel to stand this sort of work. Then came in the advantage of his railway station. What he did was to make tile top of his railway station the top of an iron girder, and the sides of the railway station the sides of a ship; so that the ship, instead of being ten feet deep, was twenty-five feet deep from top to bottom, and the strength of the ship was at the top. This at once enabled him to get an enormously strong ship with a moderately light draft of water, and to have two decks, one above the other, the upper deck being, the deck for strength, and also the most convenient deck for navigation, as well as the most preferable for passengers. There was also room for four first-class carriages outside this deck, two at each end. Here, then, was a solution of that difficulty. The next difficulty was owing to the varying hight of the water and the varying immersions of the vessel according to its loading. He had to provide for a variation of twelve feet of water, six feet one way and six feet the other way. He managed it in this simple way: He made a railway bridge of steel 60 feet long, one end supported on the land and the other end was in the air. How did he get it into the air ? Very easily. He merely put up on one side of this railway bridge a huge pillar of cast iron on the land. On the top of this pillar he put sgi?eat- cast ipoifwhoel, and round the wheel he put a chain cable. He attached one end of the chain cable to the bridge, and to the other end of the chain cable he attached a big weight half as heavy as the bridge. On the opposite side of the railway bridge he had another pillar, another wheel, another weight half as heavy as the bridge. Thus balanced, the railway bridge would remain in,the air wherever xou pleased to put it. But it was not content to stay there when the weight of the train was upon it; therefore it was necessary to keep it there by some other means, and so the chain was continued from the bottom of the weight round the wheel to a crane. When there was no weight on the bridge, f you gave a turn or two to the crane, the bridge got to the proper level; then they made fast to the cine, and the railway train Went over the bridge. That was aU; there was no merit in the contrivance. On the opposite,shore there was another bridge -hanging in the air, counterpoised by similar weights. The vessel oscillated only between those two points. - But it would be said that there must be little difficulties when the water was very high and when it was very low. Of-course there were little difficulties, but they were met by lit tie expedients. When the water was very low the bridge came a good deal over on the point of the boat and overlapped. There was a line of rail which ran down to each of the rails on the boat, and he need hardly tell a good engineer that as the boat waggled from one side to the other, he must make the bridge limp, so that it could waggle also, so that the train did not run off the rails. The bridge was made by a very good mechanical engineer, and for the life of him he could not get him to make any of his joints slack, so as to make the structure wiggle-waggle. At last he did succeed in getting him to make the holes so big for the pins that the joints could wiggle-waggle. This done, all difficulties disappeared. A good locomotive engine-man could very easily drive his engine up an incline which was not more than four or five feet in a length of 60 feet or 70 feet. True it was a deep incline, but it was so short that there could not be many wagons at a time on it, so that, while one or two wagons were on the incline, the others would be on the level; thus any ordinary locomotive engine went up the incline without knowing it was on an incline. It might be said there would be a difficulty in coming down. There was a difficulty, and he expected the railway locomotive staff would have to undergo an education. He did not know any other way of making them undergo a thorough education than by letting them make some horrible blunder. He got the company to let him have a train of the oldest wagons they possessed. He told them. secretly to make every preparation for taking the wagons out of harbor. He got the oldest locomotive engine they had, and he took care that the fireman and driver could swim. He found the brakesman could not swim, and on reflection he was glad of it, because they seemed dreadfully afraid of getting in, and the consequence was that not one of the brakesmen ever allowed a carriage to pass the chalk mark which he had drawn on the deck, because he could not swim. Having made these arrangements, the practical result was, that by beginning gradually, and going on gradually, and giving the men a fortnight to learn, by making them put in trains and take out trains every day faster and faster, first with one carriage, then with two carriages, then with three,. and ending with the locomotive engine, they at last acquired the power of doing all these things, which they thought at the beginning were impossibilities. These impossibilities were so accomplished that the term the people applied to the formidable enterprise, as they thought it, of putting a locomo-1 tive and train on boards Kinderspiel, which meant childs play. There was no merit in all this, but there was one advantage and that was simplicity. There. was no machinery required, no fixed engines, no inclined planes, no moving ma eMaeSy of an? kind; thete was Simply & railway station; m& j all the appendages on both sides were nothing more than the common appendages of a railway station. Therefore he was proud of the word Kinderspiel, These were all tke land difficulties he had to overcome; there still remained water difficulties. The water difficulties were various. In tke first place, how was he to navigate a; ship which was 320 feet long out of and into a harbor which at no place was more than double that length, and where he had to wind in a circuitous route to quays where other vessels I were b?ing unloaded ? It would be seen there was considera-I ble difficulty in the navigation. The entrance to the harbors was in one case 100 feet wide, and in the other considerably under 100 feet. Of course in a dead calm, and with no speed on, the ship could get in and out. But when there was a hurricane blowing—for though this ship did not carry sail, yet with a long train, high out of the water, she would have some sideway on her with a strong wind—the task of getting into hrbor was a difficult one. At the beginning ijwas thought this was an impossibility, and it was very near being an impossibility. When a big ship like that, drawing six feet of water, came into water six feet six inches deep, sailors said she smelt the ground. In this case she so smelt the ground i that she ceased to have any scent whatever for the the opin-i ion of the steersman or the action of the rudder; and in shallow water such as that, the steering of a vessel 40 feet wide was impossible. In order to meet the difficulty he had to teach the engineers, the steersman, and the captain/totally new lessons. He ought to mention that they haa no stem or stern to the boat; both ends were stems and both ends were sterns, and there was a rudder at both ends. There was a great dif-isalty down stairs. To say Go ahead or Go astern was fcupossible, because the engineers could not tell which end was meant for the stem and which for the stern. At last he solved the difficulty by steering entirely by the two engines and abandoning the rudder, with the following code of rules: The Gaptain stood in the center of the vessel with two tubes, one to the right engine, the other to the left engine. Out of these confined harbors they had to perform a very sharp circle to get out. But the plan they adopted was so successful that the first time they tried it ths ship went right out of this complicated harbor, which was said to be impracticable with & rudder, and with a landsman- in command. The command was given, Right engine three turns That was part of the code thatthere should never be an order given without saying when the engine was to stop, iJight engine two turns, left engine three turns ? Accordingly the vessel began to describe a curve in order to get out of the harbor. If she did not describe the curve exactly; the next command would be, Right engine two turns and a half, left engine fijpr turns. So, without ever stopping, the ship went in the exact curve, and from that day to thffe, the moment the crew had learned this power of KMinceavring, the vessel could be made to turn on a pit, s to pen-form ray number of without a rudder. TJHnrftatsgreat difficulty was got over, and the vessel now ettteriSd the harbor without ever touching a pier or touching another vessel. Next, let him say one word ae to the consequences of the construction of such a vessel. Trains coming from a great distance did not unload their goods, they went right across without delay, and the lake was now, for all practical purposes, a continuous railway. The time in putting a train on board was six minutes, the time in taking a train out was ten minutes, the time in going out of harbor was five minutes, the time in going into harbor was ten minutes, the time in crossing the sea was, the shortest, forty minutes, the longest, fifty-five minutes; so that in an hour and a quarter the whole operation was accomplished. Formerly the time occupied was two hours and a half. Need he say with regard to the heavy goods, such as machinery, engines, and boilers, that under the old system of craneage the labor of transporting them across the lake occupied several days ? . He had now to say that, whereas everybody would talk of the impossibility of making a great floating railway acrossthe Straits from Calais to Dover, there are also apparent impossibilities of every kind in the present instance, but only on half the scale. Prom Dover to Calais the distance was twenty miles; here it was ten miles. The ships proposed for Dover and Calais were 400 feet long; here they were 200 feet. The depth of water at Calais was difficult, but it might easily be made double the deptM of the water in the Swiss harbors. With regard to the sea, where the waves were gentle swelling waves, they were of no consequence; it was only where the waves were short, sharp, striking waves, that they were of any consequence. He could assure them that if a vessel were made of tlie proper size, proportion, and shape, and of the right stability for these waves, there was scarcely a constitution so delicate that would not be able to cross from Dover to Calais without any sensation almost of having been on the top of the sea. Caprlclousness of the Colors of Fish, A. C. Hamlin, in an article on Salmon Fishing in Maine, contributed to Lippincoits Magazine, for May, says; The colors of fish are very capricious, and often depend upon local and adventitious influences. The coloring matter is not in the scales, but in the surface of the skin immediately beneath them, and is probably a secretion easily affected by the health of the fish, the quality of the water in which it lives, the light to which it is exposed, and the kind of food which it eats. In the dark waters which flow through boggy moors the tints of their finny inhabitants are deep : the light silver hues change to a golden yellow, and into the intermediate shades, even to a dark orange. But in the crystal waters of the purest stream, flowing over pSbbly bottoms and white, sanda of decomposed cparta, the eolorS of the fish are very pes end tli Iwster 5s of meh brilliancy as to jjir th j appearance of transparency. We do not only observe this assimilation of color in fish to the places they frequent, but it is the same with the animals of the land. It is one of Natures provisions, and is required for safety and concealment Dr. Stark showed many years ago how suddenly the stickleback and other fish changed color when removed from dark pools and placed in white bowls. The change of hue took place with as much rapidity as though it were subject to the caprice of the fish, as is the case with the chameleon. Food has a very decided influence, and, in connection with other circumstances, will produce a marked effect in the appearance of salmopidse, even in the same lake. Thus in Lake Guarda, in Italy, we may observe one specimen with silver sides, blue back, and small black spots, and another of the same variety with yellow belly, red spots, and an olive-colored back. The like phenomena have been observed with trout of the same variety in the lakes of Germany and Ireland. Differences of food and habits, says Davy, may occasion, in a long course of ages, differences of shape and color which may be transmitted to offspring. Trout that frequent clear and cold waters, and feed much on larvae and their cases, are not only red in flesh, but they become golden in hue, and the red spots increase and outnumber the black ones; but when feeding upon little fish they become more silvery in color and the black spots increase. We have some singular examples of the effects of difference of diet. The peculiarity of feeding on shell fish produced the gillaroo trout, a remarkable variety found only in the Irish lakes. The charr also is liable to great variations from the effects of its food, and its history has in consequence been much confused by the naturalists. We observe similar effects with the corregoni, or white fish; for instance, the powan of the Scottish and the pollan of the Irish lakes. Agassiz noticed that pet parrots, when fed upon certain fish of the Amazon, changed colors, and their green plumage became spotted with yellow. Age also often causes a great difference in the appearance of fish, and the markings of the young change singularly with their growth; the Cornish sucker has two large ocellat-ed spots behind the eye, which are not visible in the young fish.