ceived very beneficial development in the past three years. From a device, which was not only very careless in its operation, but so overworked that its parts could not stand the continued strains, there emerges an instrument thorcughly reliable and not apt to lead to the engineer's increase of vocabulary. A worm-band is securely fastened to the main shaft, into which engages a worm-wheel. This latter by an exten- sion shaft carries and operates the electrical contacts fixed on a drum. The worm-wheel revolves once for every ten revolutions of the main shaft, thereby lessening greatly all strains. The electrical contacts can be so. arranged that they mark every revolution or any proportional number. The brushes, as in the other instru- ments, are of carbon.* Tenacity of Crude Methods. While great improvements are made in important large systems and ap- paratus, it is remarkable how long crude methods remain by which the desired results are attained. Contrac- tors for battleships are required to demonstrate that the vessel will under certain stipulated conditions acquire and maintain a guaranteed speed' It can be plainly seen that the greatest requisite to meet this condition is suf- ficient and constant . steam pressure. Passing from this stage the smuvoth and regular firing of the boilers. be- comes the point of vital interest for the accomplishment. of the result, of interest not only to the builder but as well to the owner, for he also desires structed on the gravity principle with that the vessel be capable at all times of producing . this guaranteed speed. Until recently the method employed was by word of mouth from the en- gine room with men calling off the time. intervals from watches, these lat- ter posted in each tire-room. Today these signals are automatically and chronologically regulated and transmit- ted from the engine room to each fire- room. The transmitter consists essen- tially of a small motor driving through gear and two steel discs a drum con- taining on its periphery contact seg- ments. Between the steel discs is placed a raw-hide pinion movable from the circumference of the disc to the center. By varying the position of this pinion the revolutions of the con- tact drum are controlled., A graduated pointer on the exterior of the water- tight case permits the interval of fir- ing from twenty seconds to ten. min- utes... This transmitter is connected by a cable of wires to the various indica- tors, one usually in each fire-room. *This instrument is now to be superseded by a direct reading instrument--designed to indicate continuously any and all speed changes, Tae Marine REVIEW These are designed to produce both aural and visual signals, 7 ¢@, a large gong and incandescent lamp. They are about 14 in. in diameter, marked eh raised letters "Fire Furnace No. -- above a small opening. a brass dial cut with the figures of the furnace numbers is revolved by a ratchet movement accomplished by magnets, as they are energized by the closing of the circuits controlled by the transmitter. In this way the num- ber appears in the opening of the in- dicator simultaneously with the sound- ing of the gong. This is the simplest system that has found favor at the present time, although there are others which, being more complicated, -- still provide the same results. The Call-Bell System. Employed for use in the officers' quarters the call-bell system is one en- tirely of comfort and convenience. The various pantries and orderlies are supplied with annunciators connected with push-buttons located in the officers' state-rooms and offices. This system divides into groups correspond- ing to the military grouping or rank of the officers. There are calls for the admiral and captain, ward-room calls, junior officers' calls and warrant off- cers' calls. Since the general change in type of installation from molding to conduit, the design of all annun- ciators, push-buttons, and accompany- ing appliances take the prevailing characteristics of water tightness. The annunciator drops are carefully con- 'stfficient safety to protect against false signals due to vibrations or gun shock. The call-bell system, which operates in conjunction with the voice- tube system, is sharply divided for military safety into exposed and unex- posed calls. In such manner the cir- cuits that may be required in the open- ing of an engagement, and thereby made useless when the conflict rises to its height, will not make unavail- able those circuits which in the in- terior of the vessel are still of vital necessity. It is the practice to dupli- cate the call, that is, that a push-but- ton and bell are required at both ends of the voice tube. As may be sur- mised, it often transpires that many voice tubes with their calling appa- ratus meet in one compartment. This leads to a system of stations located at important points throughout 'the vessel. At these stations 'it is con- venient to eroup all the voice tube mouth pieces, push buttons, bells, or buzzers and annunciator on a_ brass panel. This preserves space and pro- duces an excellent installation. The push buttons are all carefully labeled In the interior 'resent and explain them. September, 1909 so that communication can be quickly and, with the aid of the annunciator, intelligibly established. : Voice Tube. It may be written without fear of contradiction that voice tubes parallel every important system of interior communication. They are seamless hard drawn brass tubes varying in ex- ternal diameter from 1% to 4 in. Tubes wary in thickness for the purpose of mechanical strength, those | which are led in straight runs No. 20 B. W. G. and those for bends and where subject to mechanical strains No. 14 B. W. G. Where tubes con- nect two terminal points by a direct path, or of a large diameter, so that they may be utilized for shouting tubes, or when they are employed for gun firing control, they are not pro- vided with calling arrangements as above. explained. Certain of -these tubes are fitted with whistle mouth pieces in lieu of the bell and push but- ton. Mouth pieces differ in design for nearly every condition of use, and only a detailed description could fairly rep- Indeed, as new conditions arise, or more efficient ~ methods present themselves, the mouth pieces are immediately attacked and the old types ordered into exile. Be- tween compartments that are water tight special mouth pieces of water tight design are installed; between non-water tight compartments, or 'non-water tight and water tight, a sim- ple covered or open type. For shout- ing tubes, usually 3 in. or 4 in. in di- ameter, a design of the pattern of a megaphone is preferred. In the boiler rooms, where the forced draft occa- sions a disturbing pressure, the design provided is that of a diaphragm in the mouth piece, which can be only affected by the human voice. The tubes used solely for the control of gun fire are aranged so that a long flexible tube can-be plugged into the permanent mouth piece. This flexible tube ends in a headgear containing in some conditions only two ear pieces and in others the addition of a mouth piece. This design permits the men at the guns to have the freedom of their hands, at the same time receiv- ing direct aural orders from the officer in charge of the guns. It will be ob- .served later how this system thas tak- en its cue from the present adapta- tion of the telephone for this, like duty. To obtain the greatest good, from the voice tube system' extreme care is observed in all requirements of its installation. Those points of inefficiency which were indicated in the description of this system for mer- chant vessels are overcome as far as