Interchangeable arcs are manufactured which may be readily adjusted so as to operate on either direct or alternating current, and on voltages from 110 to 220. Two lamps may be run in series on 220-volt circuits.

The distribution of light, and the resulting illumination for the different lamps just considered, will be taken up later. Aside from the distribution and quality of light, the enclosed arc has the advantage that the carbons are not consumed so rapidly as in the open lamp because the oxygen is soon exhausted from the inner globe and the combustion of the carbon is greatly decreased. They will burn from 80 to 100 hours without retrimming.

Table X. Rating Of Enclosed Arcs

Watts Consumed

Mean Intensity in H. U.

Mean Watts

D. C Lamp

Current

In Lamp

In Arc

Mechanism

Spherical

Lower Hemispherical

Spherical H. U.

Lower

Hemi-spherical

OPAL

Outer

Clear Outer

Opal Outer

Clear Outer

Clear Outer

Clear Outer

235

332

2.37

1.66

1

5.01

551

401

150

172

256*

362*

3.10

2.18*

1 .52*

3

5.08

559

406

252

195

216

282

2.85

2.60

1 .99

4

4.76

524

381

143

127

139

208

4.12

3.76

2 52

5

4.16+

458

333

125

154

174

221

2.96

2.63

2 07

7

4.76

524

381

143

203

333

317

2.63

2.20

1 .65

9

4.84

532

387

145

182

226

281

2 83

2 38

1 .89

10

4.99

549

399

150

20 2

242

309

2.74

2.24

1 77

12

4.87

536

390

146

178

19.5

230

3.05

2 66

2.33

Mean

4 9

529

384

144

176

207

272

3.03

2.60

1 .98

A. C. Lamp

Current

In Lamp

Power Factor Lamp

In Arc

Power Factor Arc

Mechanism

101

6.40

448

.63

340

.82

108

127

141

206

3.52

3.17

2.17

203

236

2.26

1 .94

102

6 79

459

.61

375

.73

84

146

176+

226+

3.31

2.60+

1.72+

103

5.89

424

.65

344

.75

80

116

130

147

3.66

3.15

2.88

105

6.20

414

.61

382

.80

32

128

187

219

3.24

2.20

1 .89

153

169

2.56

2 .23

106

6.12

378

.56

298

.70

8O

132

182+

284

2.82

2.19+

1.48+

108

6.48

457

.64

383

.80

74.5

133

175

211

3.20

2.61

2.16

110

6.18

339

.49

276

.72

63

140*

126

143

2.41*

2 68

2.37

Mean

6 29

417

.60

342

.76

74.5

130

159

190

3.31

2.66

2.23

*Condition of no outer globe. +Condition with shade on lamp. H.U. Hefner Units.