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36 In connection with the Stone Lloyd system of water-tight doors, an "elec- tric indicator is fitted in the navigat- ing house which shows the position of every water-tight door in the ship. The doors are closed or opened by hydraulic power simultaneously, by the officer in charge moving a handle which operates the control valve. The function of the electric indicator is to ' show the officer exactly what doors are open or closed. The indicator has a small lamp for each door with wires led to a contact switch at the door which, when the door is closed, com- pletes the lamp circuit and lights the lamp. . Another important fitting on. bridge is Martin's automatic indicator for the navigating lamps, which is shown open and closed. The indica- tor controls five lights as shown, each light consisting of a duplicate filament lamp, one filament being lighted nor- mally. In the event of this filament failing, the armature of a small elec- tro-magnet which is in circuit is re- leased, and falls against an auxiliary .contact,, which completes a_ circuit through the remaining lamp filament and through the indicator lamp corre- sponding to the light affected. Atten- tion is also drawn to the occurrence by an electric horn attached to the indicator. On the officer in charge pulling a handle the horn ceases to sound, and the electro-magnet is in- serted in circuit with the second fila- ment; should this latter fail the horn again sounds, and cannot be stopped until the lamp is replaced or switched off. The several lamp circuits are con- trolled by the slipper switches seen under the indicator, and the latter-- as, indeed, all the important appa- ratus on the. ship--is . connected through a change-over switch from either the port or starboard feeder systems, thus guarding against a fail- ure in the navigating lights. In conclusion, I commend to ma- rine engineers and' naval architects a closer study of the advantages of elec- trical power driving for all auxiliary machinery. The question of propelling practically as much more material. the ship by electric motors awaits development, but the electrical equip- ment of the Mauretania shows many advantages over the present wasteful system of steam engines. The paper was illustrated by numer- ous diagrams. The steamer J. W. Moore, which was wrecked in the Detroit river last season and which was repaired at Ecorse, arrived in Cleveland this week from the ship yard to load coal. the ° TAE MARINE REVIEW LAKE SHIP YARD METHODS OF STEEL' SHIP | CONSTRUC- TION. BY R. CURR. An error crept in the article of the issue of March 26 and will be better explained by repeating the article frum Fig. 17. Fig. 17 shows sketch of side stringer case the butt strap must be increased in thickness to make up for the flanges of. the channel. The channel if flattened out would measure 16 inches by 7/16 inches thick and would be equal to 7 sq. in. The plate for the butt strap must have an area of section of more than 7 sq. in. arrangement. A is a 12-in. channel fast- ened to the frame with three 34-in. diam- eter rivets. A single butt strap 12/16 in. thick: is fitted in the bosom of the channel for a connection with twelve 34-in. diameter rivets for fastening same. This is the same consideration as the connection of two channels back to back, only plate is used instead of overlapping the channels which could not. be done in this case. The butt strap arrangement as. this, needs double the number of rivets and afte HE -- Fig. 18 shows a double butt strap ar- rangement which effects a saving in rivets and makes neater work. The intercostal B is of more impor- tance here than at the girders connected to the bottom plating. In this instance double clips are fitted to the intercostal increasing the number of rivets through the frame and adding to the strength of the tee at the frame channel. The butt strap A, Fig. V7, is fitted be- tween the flanges of the channel in which The punching of the channel. decreases the area of section 3% in. Example. 16% ---4..xX 13/416" rivet holes equals 13/16 X 4 = 3.25. 16 -- 3.20 = 1275.. 1275. 6% 7/16 =e 5.378 ae Butt strap equals 11" -- 3.25 for rivet holes:equals 7:75.an.. 7.75 12/16.==2-5.81 sq. in. and gives the benefit of the ma- terial to the plate for butt strap. Two pieces half the thickness would be ample in this case for a double strap and there would be a saving of six rivets as shown by Fig. 18. The double strap gives a double shear to the rivets as explained in previous articles. This example shows that a consider- ably greater loss is obtained in punching the heavier material of the same surface measure and care is necessary in com- paring the punched and unpunched ma- terials. A 15-in. strap would be ample for the butt connection A, Fig. 17, which is 18 in. wide but-no objections have been raised because of butt straps and butt laps being wider than the rule laid down by the various societies and sometimes circumstances govern the widths of butts and laps. Sometimes it facilitates the work by making the laps on the plating wide enough to cover the seam lap rivets even when four rows of rivets are needed for laps. Fig. 22 shows plan of spar deck with one side plated and the plating removed