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of conditioned air without percep- ‘tible drafts. This cooled air grad- ually sinks and is exhausted through ducts in or near the floor, and, after being cooled and mixed with a prop- er amount of fresh air, is returned to the room. A temperature differ- ential between the room and the out- side air of about 10 degrees Fahr. is generally maintained and found sat- isfactory. As the effect is felt im- mediately, it is only necessary to use the cooling apparatus during meal hours, the system being started about one-half hour before meal time and shut down immediately after the passengers leave the room. The sketch in Fig. 1 shows the type of conditioner in general use for the larger spaces such as dining rooms. The return air from the room is divided into two streams ‘‘a’ and “pb.” The return air ‘‘a’’ as well as the fresh outside air, which enters at ‘‘e’’ pass through the cooler which reduces the temperature of the mix- ture to the dew point and: so precip- itates a portion of the contained moisture which is drained off. The air emerging from the cooler is then mixed with the portion of the return air ‘‘b’’ under the influence of the thermostat ‘‘d’’ and thus warmed to the temperature desired in the room and reduced in humidity. For some installations, a portion of the cool- ing has been done by a cold brine spray, but this system has certain ob- jections for shipboard use. In cold weather a steam heating coil inside the conditioner is used instead of the cooling coil. For smaller rooms, such as suites and individual staterooms, a simpler apparatus as shown in Fig. 2 is quite adequate. In this apparatus the room air is continually recircu- lated by an internal fan and the de- sired amount of fresh outside air is admitted to the room through the regular ventilation supply terminals. While the amount of refrigeration must be calculated for each individ- ual case, based on the amount of heat generated by lights, warming tables, personnel and the incoming air, in general it will be found that one ton of refrigeration will be re- quired for about 1250 cubic feet of public room space and about 2000 cubie feet of stateroom space. While the refrigeration for the larger type of conditioners is in general supplied from the ship’s main refrigerating plant, it will probably be found ad- visable to fit small self-contained au- tomatic refrigerating machines to serve individual conditioners, es- pecially when they are at a distance from the main plant. + + ° 8 Some Examples of Arc Welded * Ship Construction, by David Arnott, member. To the American Bureau of Ship- ping, of which the author of this 14 paper is the chief surveyor, must go no inconsiderable part of the credit for the progress made in recent years in the application of are welding to ship construction. This is a very valuable review by practical example of the advances made in the use of are welding in the marine field. The paper which is 38 pages in length is profusely illustrated with both photo- graphs and line drawings of the ves- sels described. A few selected excerpts from this paper follow: Electric are welding in the ship- yards of the United States has reached that stage of development where it is rapidly becoming a seri- ous competitor to riveting in the con- struction of certain classes of mer- chant ships. In these circumstances it is felt that a paper giving partic- ulars and showing the structural ar- rangement of some small all welded ships recently built in this country would be of interest to the members of this society and will serve to pro- mote or provoke a useful discussion on a subject of increasing importance to naval architecture. The paper is written from the point of view of the naval architect whose primary interest in welding is the economics in cost and weight of material likely to be effected by the new process without sacrifice of structural efficiency, rather than that of the welding engineer. Costs, Welding, Riveting Contract price is not always a eriterion of actual cost so that only those shipbuilders with experience of building both welded and riveted ves- sels of the types described can give any real idea of comparative cost. It is probably safe to suggest that a welded barge of rectangular section can now be built somewhat cheaper than the corresponding riveted job, but that the cost differential in favor of welding will be less or may en- tirely disappear if the huil is of ship shape form, especially if the plating seams are flush, owing to the _ in- creased difficulties in erection and the. necessity for. earctul fitting. Larger vessels cannot be so readiiy assembled in pre-constructed units, and, since a greater proportion of the welding will require to be done on the ship, it is difficult to conceive of the labor cost working out less in welded ships of the ordinary ocean going type. It is perhaps a commonplace to suggest that the ship’ structure should be designed primarily for welding, but it will nevertheless bear repetition. Reducing as far as pos- sible the number of structural mem- bers and using large plates to keep down the number of joints and in- cidentally the amount of welding will obviously make for economic design. The proper place for education in welding to begin is in the technical schools or colleges from which our technical staffs are recruited. Our MARINE REVIEW—December, 1934 shipyard draftsmen should not be content ‘‘to leave it to the welder,’ but should make themselves familiar with the fundamental principles un- derlying welding design, and also keep in touch with practical develop- ments in allied industries. Electric are welding has devel- oped along sound and conservative lines to a stage where we have avail- able a method of joining structural parts which is superior to riveting. The process has come to stay and a gradual extension of its application in merchant ship construction can be confidently anticipated. Continuous research and technical investigations have resulted in a tremendous ad- vance in welding equipment and welding technique, but there still re- mains a wide field for investigation in connection with fatigue and stress concentration in welded joints. In this scientific age, we have to learn to a large and increasing extent from the experience of others, Ine tis connection valuable educational work is being done in this country by the various committees of the American Welding Society. ¢ ¢ % by Com- The Battle Cruiser, 9. (CC), mander H. E. Rossell, U.S.N., member. The author is professor of naval construction at the Massachusetts In- stitute of Technology. In this in- teresting paper he has given an his- toric outline of the development of the modern battle’ cruiser. The paper is nine pages in length anda is illustrated by photographs of the British battle cruisers, Hoop and ReE- NOWN, the first being the largest and most powerful ship of this type ever built. An artist’s sketch is also shown. of the French battle cruiser DUNKERQUE now under construction. One of the three Japanese battle cruisers, the KIRISHIMA is also shown. A very interesting analysis is pre- sented of the part played by battle cruisers in the World war. The bat- tle of Heligoland is referred to as an illustration of one of the important functions of battle cruisers in sup- porting light cruisers in an engage- ment with vessels of similar type. At the battle of the Falkland islands two battle cruisers of the INVINCIBLE class won great prestige for this type. An analysis is also made of the actions of Dogger Bank and Jut- land. In the latter instance the bat- tle cruiser demonstrated additional functions where high speed and great offensive and defensive power were of great value. In conclusion Commander Rossell states: The imminence of the termination of current armament treaties make the present an appropriate time to study merits and shortcomings of all types of warships. If past experi- ence be a reliable guide, we may ex- pect future naval wars to develop