Timber,

trestles, 113-115

approaches, 21

filling up, 113

low classification of, 415

military bridges, 465

Time,

considerations, 121

element in. war, 460

expenditure on approach grades

to bridges and tunnels, 56

factor substituted for cost factor, 461

mixing concrete, 391

repainting, determination of, 445

required for solution of

economic problems, 33

schedule of fieldwork, 380

versus material, 18

Toch Bros., 437

"Tockolith," 432, 437

Tool equipment, 374

Tools for military bridges, 477

Top-chord,

pins, location of, 204

polygonal, economic depths of

trusses with, 176, 177

Top flanges, cover-plates for, 200

Torch, use of, for cleaning metal, 441

Towers for vertical lifts, 294

Tracks, 384

electric-railway, 190

gauntleted, 128

shops, 379

Traction loadings for old bridges, 412

Traffic, 20

congestion at entrance and exit, 54

diversion of, during replacement, 405

investigations, 20

pedestrians on transbordeur, 323

probable, 20

several kinds on one deck, 128

tunnels, stoppage of, 57

Trains, thrust of braked, 140

Transbordeur,

author's improvements on, 320

comparative operating capacity,

328, 330

conditions favorable for, 330

description, 318

efficiency, 330

general conclusions concerning the

economics of, 335, 336

Havana Harbor, proposed, 332-334

high-level bridge comparison, 330

improvements on present type

of, 319, 325-328

inferior features of, 318

New Orleans, description of, 321-323

ordinary, description of, 319

Philadelphia and Camden,

proposed, 335

possibilities and economics

of, 318-336

Transbordeur,

summary of conclusions on

economics of, 320, 321

time schedule, 324

types of truss suitable for, 319

velocity of cages, 323

Transformers, 312

Transportation,

materials for military bridging, 482

unnecessary, elimination of, 366

Transporter bridge, 318

Travel, automobiles in tunnels, 53

Travelers, expensive for deep trusses, 176

Treated lumber unsatisfactory for

sidewalks, 426

Treated ties, economics of, 182

Treatment of men, 385

Treatment of steel to be encased, 443

Treatment of timber, 183, 188

Trestles,

approaches, timber, 21

double-track railway, 252

economic span-lengths, 250-256

highway, economic span-lengths

of, 252

military bridges, 467

pedestal costs affecting

economic layouts, 252

reinforced-concrete for steam

railways, 230

span-length, economic, for

military, 465

steel, economics of, 250-256

versus reinforced-concrete, 114

Triangular trusses, divided, for continuous

spans, 78, 80

Triangular versus Pratt trussing, 71

Trimming and cutting metal, 374

Troubles, anticipating, 371

Trough floors, 182, 214

Truck loadings, 125

Trucks, great weight of, 425

True economy, development of, 2

Trunnion bascules, 290

Trusses,

bridges, economic span

lengths for, 150, 165

crescent, 272

criterion for alloy steels, 27, 28

depths, economic, for parallel

chords, 176

depths, economic, for suspension

bridges, 265

depths for cantilever bridges, 259

doubling of, 21

economics of, 175-181

spacing, 186

Tullock, A. J., 439

Tunnels,

almost always more expensive than

bridge, 54

automobile travel in, 53