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THRE MARINE RECORD, 2 1 aa This tends to show that the extensions and compressions are directly proportional to their distance from the neutral axis, This and similar experiments tend to prove that for all practi- cal purposes, the strained section of any combination of mal- leable iron plates may be considered subject to the following principals: 1. The neutral axis passes through the centre of gravity of the section. 2. The same force is required to extend as to compress a given section of iron by the same fraction of its length. 3. The extension and compression at a given point is di- rectly as its distance from the neutral axis, and hence, the force exerted by a small portion of the area at that point is directly as the area considered, multiplied by its mean dis- tance from the neutral axis. The force of a small portion of the section given multiplied by its distance from the neutral axis, is the amount of that small! area, or, in other words, it is the leverage which that small portion opposes to the leverage tending to rupture the entire section. Gentlemen, such simple calculations as these may become both interesting and instructive to practical shipbuilders, and for those who desire to study the subject closely, I may refer them to a paper by the late professor Jenkins, and to Mr, W. H. White, F. R.S. To illustrate how very useful this has been to me, I may tell you that when I was designing this steamer, I placed that girder almost like it is now, and looking at it ina practical way, I thought it represented ample strength for the guowale, but when tested by these figures, it was found want- ing ina high degree, this brings out the statement that you will find it a difficult problem to make a serviceable, strong and shallow steamer fit to carry even four thousand gross tons of cargo on 14 feet draft of water over these lakes, without resorting to the overhead arch, such as I illustrated in a local paper about a year ago, for by these calculations I found that large and heavy as that girder was, it was then connected to the design for a hull that could only have occupied the lowest position as regarding longitudinal strength amongst the vessels named in the annexed paper. So [ immediately added a thick doubling plate to the top plate, and increased the plates and angles connecting the sume to the turn-over plate in a proportionate ratio, and now it may do. Mr, Fairbairn proposed plating over the upper deck beams at the sides of the hatches, so as to make the section of iron at the deck equal to the section at the bottom, though all our deep steamers would be the better for two steel decks, I du not mean that such are required to resist the longitudinal yer- tical strains to which ships are subject, but rather to resist panting and racking strains resulting trom external pressure and consequent reaction. I must now ask you to dismiss from your minds the idea of the fixed beam or girder for the no- ment, and look at the structure of a’ship, in a more general way as I intend to prove to you that, for the purpose of strength, we are in the habit of placing, our one metal deck, (when only one is fitted) in deep steamers, on the wrong tier of beams, you know that even in still water, there is great pressure on the sides (this amounted to about 4,000 tons in the‘‘Great Eastern’”’ as well as on the bottom, tending to collapse the structure, the bottom, or rather, (the combination of bottom and double bot- tom) has to put forth, but a little of its strength to resist such pressure, but when we come to tke sides, and particularly the top sides, we do not generally find such surplus strength to re- sist this pressure. When the vessel rolls ovec on to her beam ends, her sides very largely assume the normal position of the bottom when a great portion of the total weight of hull and cargo must be borne by the sides of the vessel, now when there are nu metal decks, and but poor stringer plates, the beams may bend and twist, or buckle, and the whole upper works become strained, for remember that when there is external pressure and compression on one side, there will be corresponding internal pressure on the opposite side, the difference in pressure alone being frequently as much ag 20 to 1, and the righting moment perhaps 15,000 foot tons, and with such stresses alternating several times per minute, it may be, it should seem that the sectional area of deck plating ought not to be so much less than the external bottom platings as is too commonly the case. In these deep but shallow draft steamers, you will ubserve that the severe pressure on the side may seldom, if ever, reach the upper deck beams with any intensity if there be two decks, and so if the main deck only be made strong und the upper deck and top-sides be well con- nected to it, by deep, though thin, web plates, there need be no straining of the upper decks for the main deck will receive the main thrust and pull. Now I believe this to be so over the greater portion of what is practically the mid-ship body of our steamers, but when we approach the ends, (particularly the after end), as our steamers are constructed, the physical conditions connected with buoyancy and weight are changed, and I aver that the stresses we ought to anticipate most carefully will not attack the mid-ship body at all, but will be found where the great weights are unbalanced, for instance about the location of the fore end of the boiler house, and let me add that straining in these ports is more likely to occur when the steamer is light than when loaded, for the discrepancy between buoyancy and will then be the greatest, is it not your experience that My part boiler room, part hold than in any other locality, and cer- tainly more frequently there than about the position of the centers of gravity and buoyancy, Further I may say that when ‘a ship rolls onto her beam ends, the angle forming the junction between the top sides and deck endeayors to alter its form, the angle on the immersed side would become more acute and that on the immersed side more obtuse, to avoid this straining action I have for a long time recommended that muci broader web-plates be fitted be— tween the main and upper decks, indeed I would make the web-frames just the reverse of what is common, viz: broader a‘ the top than at the bottom. It would seem that most of the shallow places on which our lake steamers ground, is rocky, or at least very hard and solid ground, This being so, in my opinion it would be worse than useless to attempt making the bottoms of steamers strong enough to withstand ordinary grounding, without sufiering ma- terial injury, and if this be so, I think the best g thin will be to arrange the construction of ships bottoms, so that they may be quickly and cheaply repaired, which I believe can be done without any sacrifice of strength, With this object in view, I propose to construct the bottom of comparatively small pieces, for instance in my novel steamer (which is 316 x 40x 20, I make the longitudinals each 18 x 7-16) spaced 4 feet apart, one will be rivitted to the outer bottom, and one to the inner bottom, the connection between the two being affected by vertical angles and bracket plates spaced 3h feet apart, these bracket plates will, of course, be connected by thwartships, angles to the upper and lower bottoms, the latter angles taking the place usually occupiedby the transverse frames. I need not weary you with any further description of my system, as the illustrations annexed should make my proposed arrangement fairly clear, as regards the bottom plating, which is really according to my experience, the most interesting feat- ure in our steamers (to an underwriter at least) let me explain that instead of lapping one stroke of plating over two others, I plate the bottom flush, which gives edge to edge plating, this necessitates 9 narrow fore and aft strap, which will be single riveted,some people may fear this, but let me briefly state that in all my experience Ihave never seen any evil results from single riveted longitudinal seams in ships, and I have often examined ocean vessels of tweuty or thirty years of age with such seams single rivetted, indeed the ‘Great Eastern’? was only single rivetted in longitudinal seams, and such showing no indications of straining, but were perfectly eligible for continu- ation in the highest class. (Lo be Continued.) ro A FLOATING CHURCH, In Brooklyn, N. Y., a dismantled bark is moored to the stringpiece of the dock by heavy chains. Upon her main deck forward has been constructed a chapel, and within the six pillars that support the roof hangs a large bell which is used to call together the congregation of sailors from the sur— rounding shipping, who three times a week assemble there in worship. For 20 years the craft has been used asa Bethel ship, and the hull is staunch, and copper fastened, so it is not without the bounds of possibility that she may be rigged and sail the seas azain. The bark has an exciting history. She was built and com- manded by Capt. John Tam, who is well remembered by old whale-men, who speak of him as one of the oldest and most successful of whalers. For years he commanded a 500-ton brig, but she was sunk by a whale and then he hada bark built of live oak and hackmatack, in Belfast, Me. He and his crew made fortunes in this vessel, and in 1865 he retired, In 1869 the bark changed into a propeller, and made her ap- pearance as an East India trader. Like most whaling ships, her bull was saturated with whate oil, which isa great pre- servative of wood, She was purchased by a Norwegian beneyo- lent society to be used as a Bethel ship, and was made fast to pier 11, North River, where she lay for 17 years as a floating church for Norwegian, Danish and Swedish sailors, There she remained until 1886, when she was towed to Brooklyn and made fast to the pier at the foot of 36th Street. MOORING GROUND AT THE WORLD'S FAIR, Commodore George W. Gardner, of the Inter Lake Yacht- ing Association, speaks to the point jin suggesting that pro- vision be made for the accommodation of yachis during the Fair next summer. {He said that protected anchorage ground should be provided for yachts by the construction of a break- water. The basin should be dotted with numbered buoys, to which the boats might be made fast. Persons desiring to take edyantage of the anchorage ground should make application giving dimensions of their boats and they could be assigned accordingly. Space could be economized by arranging the boats according to the size. He also suggested that races should be arranged and prizes offered for boats of various classes. ‘If that were done he believed that yachts represent- ing all the great maritime nations wouldjattend the Fair, ‘It would be a wonderful sight to see two hundred yachts an- chored there at night,”’said‘Mr. Gardner. ‘They would, of course, be brilliantly illuminated, and it would be one of the more of our steamers complain at this nondescript pvint | great attractions at the Pair.” A LOCAL INSPECTORS INQUIRY. The New York local inspectors or steam vessels Samuel G. Fairchild and Thomas H. Barrett have been trying to hold an inquiry to find out who was responsible for a collision oc- curring in the Harlem River, The result of the local inspector’s investigation, in which five witnesses from the tug and four from the steamboat, in- cluding the captains of each were examined, was that Cap- tain Harper’s license of Transfer No, 4 was suspended for ninety days, and Captain Peck’s for forty-five days so that one was exactly half as much to blame as the other. Captain Har- per’s license expired thirty days after he was suspended, but Inspector G. Fairchild, when reminded of this, refused to alter the decision, Captain Harper says, and, although the law for- bids the suspension of a pilot for a longer time than his lieense runs, the decision was allowed to remain on the books of the Board. The New York Herald, of June 25th contained the fol- lowing interview: ‘‘Can’t anybody make me believe he didn’t see the City of NorwaJk’s port light,” said Inspector Fair- child. “Allowing that Captain Harper was steering in the direc- tion he testified would that have justified him in blowing two whistles and keeping ahead?’ I asked. “No, sir,” was the reply; ‘I don’t think he had any right to biow two whistles. He should haye answered Captain Peck and gone to port ot him.’’ “Yet you say in your report to the supervising inspector:— “If the green light of the City of Norwalk was alone visible to the crew of transfer No. 4, which the position of the vessels and the course of the channel would make improbable a blast of two whistles would clearly have indicated the wishes of the master of the tug?’’ “I didn’t say he should blow two whistles, I don’t think Ieaid two whistles,” declared Inspector Fairchild. Then he hauled out the minutes of the investigation, and there was his letter with the quotation given from it. “Well, I don’t think he would have been justified ir. blow- ing two whistles,’ insisted the inspector, ‘I told Captain Peck privately what I thought of the matter.” ‘‘How do you account for the suspension of Captain Harper for ninety days when his license expired in thirty days and when the law forbids it?” ‘Well, if he’ll come here when his license has expired he’ll get it back if there are no other charges against him.” “Did you ever hear of Captain Peck being treated for color blindness?” “No, sir, Ididn’t. [ have never had any knowledge of that, and if it is so I don’t know it.” On the record book of the dispensary of the Marine Hos— pital on the Battery appears this entry, under date of May 19, 1880: Solomon Peck, aged forty-seven: American seaman thirty- seven yvars, steamboat City of Norwalk; incomplete color blind, but able to distinguish between signal lights when they are in their normal condition. “Do you believe, inspector, that it is always possible to obey every rule and regulation laid down? For instance, you have a rule providing that a pilot shall blow a whistie when— ever another vessel is within half a mile cf his craft. How is it possible to carry out that rule in New York harbor,'where vessels are passing and repassing one another all the time?” The inspector had to admit that this was so and that to attempt to carry out the rule would leave to confusion, Every pilot I consulted on the subject of the local inspee- tor’s decisions was emphatic in his denunciatiyn of the secret proceedings of the Board. SE THE DICTATOR OF COMMERUn, The commerce of the world originated in Asia; it was car- ried to Africa, and thence to Europe, and from Europe to America. This movement can go no further westward, foron the other side of the Pacific is China, which has successfully resisted every attempt of the European to encroach upon her domains, and India, with its teeming population of 250,000,000, so that the United States now receives the wealth of India and Asia pouring into it from the west, and the manufacturers and populations of Europe from the East, and in the near-by fu- ture she is destined to dictate to the commerce of the world and direct the channels thereof. The limit of steam power has not been reached. Electricity has just begun to offer new opportunities to commerce. We are no longer compel'ed to carry our factories to the water power, for by the electric wire the power may be brought to the house of the operative, and we may again see the private workman supersede the factory operative. A few cars and small vessels are moved by elec: tricity—the forerunner of great things. We know little of this new agency, but in fnture growth must be more rapid and more wonderful than thatfof steam, The Secretary of the Smithsonian Institute says that before the incoming of the twentieth century wrial navigation will be an established fact. ‘The deeper insight we obtain into the mysterious workings of nature’s forces,’’ says Siemena, ‘the ; more we are ccnvinced that we are still standing in the vesti- bule of science, that an unexplored world still lies before us; and however much we may discover, we know not whether — mankind will ever arrive at a full knowledge of nature.’? Tue contract for patrolling St. Mary’s River will exp July 1, and as far as can be learned no appropriati fy been made to continue the work. The matter demands immediate attention of the department under whose c re conservancy of navigable waterways and buoys, beacons are placed. ; a