are as nearly proportional to the e.m.f. as they are in other deflection instruments.

Albert F. Ganz: By deflection, do you mean the width of the reflected band of light? Is that what measures the vibration? Frank Wenner: Yes, that reflection can be brought back on the transparent scale and read in divisions.

George F. Sever: Up to what specific point can that band be used in connection with the sensitiveness of the reading and the accuracy of the reading of the instrument?

Frank Wenner: I have used it up to a few centimeters, but then only in determining some of the constants of the instrument, and was not, at that time, concerned with it as a deflection instrument. Ordinarily, the deflection is very small when it is used in the usual way.

N. Monroe Hopkins: Is the band quite distinct on the right and left edge respectively?

Frank Wenner: It is very distinct. When the band spreads out to considerable width it has this effect: it is very sharp on the extreme edges, and corresponding to the width of the filament of the lamp, or other source of illumination, it is comparatively bright, and from that it gradually shades off until you have nothing in the center.

John D. Ball: If the deflection is only a few centimeters is there not a correction for the width of the beam-the beam in zero position?

Frank Wenner: The source of the light that we ordinarily use is a filament from a lamp and focus it as sharply as possible. When you come to a very small deflection you might not be able to read it very definitely, and it would be necessary to read it not from the extreme edge, but from what corresponds to the center of the filament on each side of the image.

M. G. Lloyd: When you have the frequency adjusted to correspond with the natural frequency of the instrument, what relation is there between the deflection and current?

Frank Wenner: It is directly proportional either to the current or the voltage.

INDEX

PAPERS AND DISCUSSIONS

Air Gap Flux Distribution in Direct-Current Machines. (Il-
lustrated.) (Charles R. Moore.). .
Application of Automatic Selecting Devices to Telephone Multiple
Switchboards, The. (Illustrated.) (Alfred H. Dyson.).
Arc VS. Tungsten Street-Lighting in Small Towns. (C. E.
Stephens.)....

509

405

339

Automatic Private Branch Exchange Development in San Fran-
cisco. (Illustrated.) (Gerald Deakin.).

365

Central Station Electric Power for Railroad Operation. (Il-
lustrated.) (Frederick Darlington.).

Central Station Power in Coal Mines. (Illustrated.) (W. A.
Thomas.)..

69

1

Characteristics and Applications of Vibration Galvanometers.
(Frank Wenner.)..

1243

Characteristics of Protective Relays. (Illustrated.) (E. M. Hew-
lett.)....

175

Compression Chamber Lightning Arrester and the Protection of
Distribution Circuits. (Illustrated.) (E. E. F. Creighton and

F. R. Shavor.)..

811

Convection and Conduction of Heat in Gases, The. (Illustrated.)

(Irving Langmuir.)..

1229

Corona Losses Between Wires at High Voltages. (Illustrated.)
(C. Francis Harding.)

1035

Debt We Owe to Henry as a Scientist, The. (Michael I. Pupin.).. 1019
Design of Telephone Pole Lines for Conditions West of the Rocky

Mountains. (Illustrated.) (A. H. Griswold.)...
Direct-Current and Alternating-Current Mill Motors for Auxiliary
Drives. (Illustrated.) (Brent Wiley.)..

427

605

Does it Pay the Average Coal Mine to Purchase Central Station
Power? (Illustrated.) (Graham Bright.).
Economies of Railway Operation. (Illustrated.) (F. E. Wynne.).
Electric Braking of Induction Motors. (Illustrated.) (H. C.
Specht.)...

737

203

627

Electric Strength of Air-III, The. (Illustrated.) (John B.
Whitehead.).

1093

Electrical Characteristics of the Suspension Insulator. (I1-
lustrated.) (F. W. Peek, Jr.)..

907

Electrical Control of a Large Mine Hoist.
Cheney.)....

(Illustrated.) (H. W.

685

Electrification of a Reversing Mill of the Algoma Steel Company.
(Illustrated.) (Bradley T. McCormick.).

645

Electrolytic Corrosion of ion by Direct Current in Street Soil.
(Albert F. Ganz.).....

1167

Freight Train Tests on an Electric Interurban Railway. (Il-
lustrated.) (S. T. Dodd.).

1001

Frequency. (Illustrated.) (D. B. Rushmore.)

955

Law of Corona and the Dielectric Strength of Air-II, The.. (II-
lustrated.) (F. W. Peek, Jr.)..

Human Accuracy; Multi-Recorder for Lightning Phenomena and
Switching. (Illustrated.) (E. E. F. Creighton, H. E. Nichols
and P. E. Hosegood.).

825

1051

Measurements of Voltage and Current Over A Long Artificial
Power-Transmission Line at 25 and 60 Cycles per Second.
(Illustrated.) (A. E. Kennelly and F. W. Lieberknecht.).
1131
Metallic Tungsten and Some of Its Applications. (W. D. Coolidge.). 1219
Method of Studying Power Costs with Reference to the Load Curve
and Overload Economies. (Illustrated.) (George I. Rhodes.).
Notes on the Use of Alternating-Current in Unloading Coal. (Il-
lustrated.) (W. N. Ryerson and J. H. Crane.)...
Notes on Underground Conduits and Cables. (Illustrated.) (C. T.
Mosman.)...

Operation of a Large Electrically Driven Reversing Rolling Mill.
The. (Illustrated.) (Wilfred Sykes.).
Operation of Two Alternating-Current Stations through Parallel
Circuits and the Distribution of Load and Wattless Currents
Between Them. (Illustrated.) (J. W. Welsh.).

Ozone: Its Properties and Commercial Production. (Illustrated.)
(Milton W. Franklin.)........

Plant Efficiency-An Analysis of the Losses of a Hydroelectric Sys-
tem. (Illustrated.) (J. D. Ross.).
Practical Joint Pole Construction.
donald.).

(Illustrated.)

Propagation of Impulses over a Transmission Line.

(J. H. Cunningham and C. M. Davis.).

81

709

755

659

449

985

471

(J. E. Mac-

491

(Illustrated.)

887

231

Relation of Central Station Generation to Railway Electrification
The. (Illustrated.) (Samuel Insull.)..

Relation of Electrical Engineering to Other Professions-President's
Address. (Gano Dunn.).

Relative Costs and Operating Efficiencies of Polyphase and Single-
Phase Generating and Transmitting Systems. (H. M. Hobart.)
Self-Starting Synchronous Motors. (Illustrated.) (Carl J. Fech-
heimer.)..

Simplification of Electrothermal Calculations; The Watt and
Thermal Ohm. (Carl Hering.).

1027

115

529

1191

Some Features of the Outdoor Electrical Installation. (Illustrated.)
(F. C. Green.).

323

Some Mechanical Considerations of Transmission Systems. (Il-
lustrated.) (T. A. Worcester.).

897

Some Notes on Isolated Plants. (Illustrated.) (Percival R.
Moses.).

15

Some Problems of High-Voltage Transmission. (Charles P. Stein-
metz.).

167

Studies of Protection and Protective Apparatus for Electric Rail-
ways.
(Illustrated.) (E. E. F. Creighton, F. R. Shavor and
R. P. Clark.)....

851

Thirty Years' Progress in the Electric Furnace. (F. A. J. Fitz-
Gerald.)

1179

Vacua. (W. R. Whitney.).

1207

Hering, Carl, Paper, 1191; Discussion.. 1177, 1188, 1202, 1203, 1204, 1241

Hewlett, E. M., Paper, 175; Discussion.

196, 931

Hillebrand, W. A., Discussion...

355,

462

Hobart, H. M., Paper, 115; Discussion.. 143, 144, 146, 151, 152, 161,

1242

Hopkins, N. Monroe, Discussion.

1256

McCormick, Bradley T., Paper, 645, Discussion.
McKenney, Lester, Discussion..

McNaughton, Andrew, Discussion (Illustrated).
Miller, A. A., Discussion..

1177, 1242

1128

619

643

308

56,

283

1131

107, 932

353,

354

295

.446, 485, 503

1256

198

458

505

934

108, 192, 314

707

358

53

192, 469

933

303

598, 653, 656

462

934

.354, 357, 361