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Specialties^^ G. A. Dunham Company General offices: Dunham Bldg., 450 East Ohio St., CHICAGO, ILL Factories: Marshalltown, Iowa, Michigan Citt, Indiana, U. S. A., and Toronto, Ont., Canad Eastern Dirisioo Offices 101 Park Avenue, New York Foreign Division Offices 101 Park Avenue, New York (Japan) Uchida Trading Co., Tokyo and' New York (China)--except Darien--Pacific Trading Co., Shanghai Western 232 MonaHn^wS9.^ San CISco. Calif. Albant, N. Y., 304 Home Savings Bank Bldg. Allentown, Pa., 11 S. Fifth St. Baltimore, Mo., 218 Water St. Banco*. Maine, 104 Exchange St. Boston, Mass., 136 Federal St. Buffalo, N. Y., 232 Delaware Ave. Caldwell, Ohio, 827 West St. Clarksburg, W. Va., 300 Stealey Ave. Erie, Pa., 3302 W. Lake Road . Atlanta, Ga., 809 Forsyth Bldg. Birmingham, Ala., 812 Martin Bldg. Charlotte, N. C., 1103 Queens Road SALES OFFICES EASTERN DIVISION Harrisburg, Pa., 2216 N. Fifth St. Hempstead, N. Y., Hempstead Bank Bldg. Huntington, W. Va., ' 714-716 Union Bank Bldg. Kingston, Pa., 302 Kingston Corners Bldg. Newark, N. J., 972 Broad St. New Haven, Conn., 414 First National Bank Bldg. SOUTHEASTERN DIVISION Chattanooga', Tbnn., 1201-03 Volunteer Bldg. Greenville, S. C., 317 Walker Bldg. (P. 0. Box 563) New York. N. Y,, 101 Part A POUGHKEEPSIE, N. Y,, SOM^st Providence R l., 49 WestaS^, Rochester, N.Y., 972 MTOaSu. Stbaccsb, N. Y., 306 O.CS B PW Trenton, N. J,, 219 E. Hanover s- 8' Washington, D. C,, 327 MunsevBU. Wkiie Plains, N. Y,, 36 Avi.' Jacksonville, Fla., 4510 Sappho Memphis, Tenn.. 355 Madison Ave New Orleans, La., 419 Maritime Bldg CENTRAL DIVISION Special Sales Office. 460 East Ohio Street, Chicago, C. B. Rotate Akron, Ohio, 1175 La Croix Ave. Cheyenne, Wyo., 430 Boyd Bldg. Chicago, III., 450 E. Ohio St. Cincinnati, Ohio, 1231 Union Trust Bldg. Cleveland. . Ohio, 430 Terminal Tower Bldg. Colorado Springs, Colo., 115 E. Washington St. Columbus, Ohio, 85 E. Gay St. Dallas, Texas, 408 Dallas National Bank Bldg. Davenport. Iowa, 305 Security Bldg. El Paso, Texas, 401 N. Santa Fe St. (P. 0. Box 512) Kalispell, Mont., Whipps Block LosAngeles, Calif., 617 W.Seventh St. .Denver, Colo., 414 W. Colfax Ave. Des Moines, Iowa, 710 Old Colony Bldg. Detroit, Mich., 2988 E. Grand Blvd. Duluth, Minn., 316.Glencoe Bldg. Grand Rapids, Mich., 425 Murray Bldg. Houston, Texas, 911 Electric Bldg. Indianapolis, Ind., 325-326 Board of Trade Bldg. Ironwood, Mich., 6 Albert Bldg. Joliet. III., 309 Sterling Ave. (P. 0. Box 1086) .AHnunu g. 1UU., uu Vn-ity Bank Bide. Louisville, Ky.. 1342 StarU Bldg. 'Milwaukee, Wis., 1148 Empire mdg. Minneapolis, Minn ,132 South lotbSt Oklahoma City, Okla., ' ^ XT Omaha, Neb^ .710 N. Hudson St 724-725 Union State Bank Bldg St. Louis.. Mo., 3605 Laclede Ave. San Antonio, Texas, 3005 Smith-Young Tower Toledo. Ohio, 1914 Vermont Ave. ' ' Wichita, Kans., 1100 E. Douglas Ave. WESTERN DIVISIOaV Portland, Ore., 1000 Guardian Bldg. Seattle, Wash., Exchange Bldg. Salt Lake City, Utah, Spokane, Wash., .204 Dooly Bldg. San Francisco, Calif., 232 Monadnock Bldg. Sun Life Assurance Bldg. C. A. Dunham Co., Ltd., 1523-41 Davenport Road, Toronto, 4, Ont., Canada. C. A. Dunham Co., Ltd., (of The United Kingdom) 18 St. Thomas St., London, S.E., 1, England. . Sates Offices: Calgary, Alberta; Halifax, N. S.; Montreal, Que.; Ottawa, Ont; Toronto, Ont.; Winnipeg, Man.; Vancouver, B. C.; Quebec, Que.; St Johns, Newfoundland. . Agencies: Birmingham, Eng.; Leeds, Eng.; Liverpool. Eng.; Newcastle-on-Tyne, Eng.; Glasgow. Scotland; Belfast, Ireland; Parisi France; Munich, Germany; Copenhagen, Denmark; Gothenburg, Sweden; Wellington, New Zealand.. This Service is delivered through over eighty Sales Offices throughout the United States, Canada and the United Kingdom. These Branch and Local sales offices bring Dunham Heating Service as close to your office as your telephone. Consult your telephone directory for the address of our office in your city. An engineer mil counsel with you on any project. DUNHAM DIFFERENTIAL VACUUM HEATING SYSTEM Heating with Steam of Variable Temperatures--Cool Steam (133 deg. fahr.) Warm Steam (133 deg. to 212 deg. fahr.); Hot Steam (Above 212 deg. fahr.) Principles and Design summed up in the statement of its object-- The principle of the Dunham Differen tial Vacuum Heating System is based on the fundamental laws of heat flow and heat processes. The basis of the theory is briefly to maintain steady temperatures inside a building throughout the heating season, ir respective of the daily and hourly fluctua-tions of the outside weather. 804 Dunham Company Specialties, Heating Complicated Equipment Required Differential Vacimfi" Heating System ac- Airplane Ale Rec. 38,704 By Lieut. McCrcad? Duahtn>Dif.Sr*t.(37,861) 1 T| rDim Mft Dif prw tial Vac urn HP itinis tpir 'N lw tter Boilt t 33 C fgr( . Implishes this without : 2v complicated or deb ate equipment, or any Ml McKinley 20,000 167.3' greater variety of appliLces than is used by the ordinary Vacuum Return - Line Heating System No ' larger or special Boiler is Pike'* Peak Ml Hood 14,180 179.6' 11,22$ 186.1' 5,279 199.7 O 212.0 N. required on this system Pig. 1SS0A -than on,any other. Any type of Boiler suitable for heating work and No new principle is used to attain the 'of high efficiency can be used. long sought combination of comfortable heat, with real economy. The application Easily Adaptable to Change-over From of the Dunham Appliances which utilize Existing Vacuum Return this important principle is the only thing Line Systems new. These appliances are attention--com An ordinary, well-designed, Vacuum Re turn Line System can be changed-over to the Dunham Differential System. Radia tion does not have to be disturbed.and in most instances existing piping may be used with only slight changes. /. The system uses, steam as a heating medium. Steam is supplied at variable temperatures from 133 deg. up to 212 deg. and higher if so required. The 133 deg. temperature corresponds to 25 in. of vacuum (at sea level), and 212 deg. to zero oh the gauge. By furnishing steam at this wide range of temperatures, it is possible to vary the heat output of the radiation thus preventing overheating. pelling and revolutionary. They have made the Dunham Differential Vacuum Heating System the outstanding heating develop ment of the decade. The temperature of the steam is gov erned by the Dunham control equipment and the Dunham Differential Vacuum Pump, which removes the air from the sys tem, thereby reducing the pressure on the water in the boiler, or causing the steam to expand through Reducing Valves when they are used. The term "Differential" is applicable because a relatively constant differential in pressure between the radiator and the return is maintained, so that the air and water will constantly flow out of the radia Based on Bed-Rock Laws of Physics tors. The steam is induced to completely fill them. Due to this "Differential" com plete circulation is obtained and the radia This system is simple in design, easy to tors throughout the building are heated . install and very economical in operation. uniformly. The Heat Emitted By A Radiator Depends OnThe Temperature Difference Between The Radiator And The Air Of The Room. zia.s'Fj Heat Emission from Radiation Under Vary ing Pressure and Tem peratures The heat given off by the radiator is proportion al to the difference in temperature between the room and the; radiator. By varying the tempera ture of the radiator, the building temperature can be kept constant, and the heat given off by the radi ator kept in proportion to the heat loss from the building. By operating the system at varying de grees of pressure or vac uum the temperature of 805