CONTENTS.

Part E.

ON THE

PRINCIPLES AFFECTING THE CAPACITY AND

RETENTIVENESS OF STEEL FOR THE MAGNETIC CON-

DITION; WITH THE DEVELOPMENT OF PROCESSES

FOR DETERMINING THE QUALITY AND DEGREE OF

HARDNESS OF STEEL.

CHAPTER IV.

THE DETERMINATION OF THE RELATIVE STRENgth, or

TENACIOUSNESS OF THE MAGNETIC CONDITION, IN

EACH OF A SERIES OF APPARENTLY SIMILAR PLATES

OR BARS OF STEEL

PAGE

-

35

CHAPTER V.

THE DETERMINATION OF THE RATIO OF THE POWER OF

MAGNETS, WITH THE AUGMENTATION OF THE THICK-

NESS OR MASS, IN OTHERWISE SIMILAR BARS; WITH

THE MODIFICATIONS OF SUCH RATIO BY DIFFERENCE

OF TEMPERING

CHAPTER VI.

THE DETERMINATION OF THE RELATIVE DEGREE OF HARD-
NESS OR TEMPER, of PLATES OR BARS COMPOsed of

THE SAME KIND OF STEEL

47

65

CHAPTER VII.

THE DETERMINATION OF THE QUALITY OF BARS, PLATES,

OR INSTRUMENTS CONSTRUCTED OF STEEL

74

75

Sect I. For the determination of the quality of the unmanu-
factured or raw material

Sect. II.-Applicability of the principle, now proposed for

testing the quality of steel, to instruments, and other

manufactured articles

CHAPTER VIII.

INFERENCES, FROM THESE INVESTIGATIONS, CONCERNING

THE PHENOMENA OF MAGNETISM IN STEEL, AND ON

THE APPLICABILITY OF THE RESULTS TO THE IM-

PROVEMENT OF MAGNETICAL INSTRUMENTS

·

88

Part EE.

INVESTIGATIONS CONCERNING THE LAWS OR PRINCIPLES

AFFECTING THE POWER OF MAGNETIC STEEL PLATES

OR BARS IN COMBINATION, AS WELL AS SINGLY,

UNDER VARIOUS CONDITIONS AS TO MASS, HARDNESS,

QUALITY, FORM, ETC., AS ALSO CONCERNING THE

COMPARATIVE POWERS OF CAST IRON.

CHAPTER I.

PAGE

AS

TO THE POWERS OF COMBINATIONS OF MAGNETIZED

PLATES OF TEMPERED STEEL IN CONTACT

RESULTS

· 97

- 109

CHAPTER II.

ON THE POWERS OF

COMBINATIONS OF MAGNETIZED

STEEL PLATES, SEPARATED BY LIMITED SPACES

RESULTS

CHAPTER III.

ON THE RELATIVE POWERS OF COMBINATIONS OF MAG-

-

119

- 128

NETIZED STEEL PLATES OR BARS, AS AFFECTED BY

DIFFERENCES IN THE DEGREE OF HARDNESS OR

NATURE OF THE TEMPER

132

Sect. I. Of the relative Powers of Combinations of Magnetized

Steel Plates, as affected by changes in the TEMPER of the SAME

SERIES of Plates

-

133

Sect. II. Of the Magnetical Powers, separately, and in combi-

nation, of Steel Plates variously tempered, both in extent of

surface, and in degree of hardness

153

Sect. III. Of the Magnetic Powers of Combinations of very hard

Plates and Bars

1. As to hard Plates

2. As to hard Bars in combination

RESULTS

. 159

- 168

- 175

159

CHAPTER IV.

ON THE RELATIVE POWERS, IN COMBINATION AND SEPA-

RATELY, OF HARD PLATES OR BARS OF STEEL OF

DIFFERENT DENOMINATIONS AND QUALITIES -

PAGE

· 185

Sect. I. Of the Magnetical Powers, in combination, of Steel

Plates (7.5 inches in length) of different denominations, but

of the same original quality of Iron

1. Experiments with Steel of different denominations,

converted out of Stubs's Steel

-

189

· 189

195

2. Experiments with Steel of different denominations,

converted out of best Swedish iron, marked hoop-L

Sect. II. Of the Magnetical Powers, in combination and

separately, of Steel Plates (7.5 inches in length) of similar

denomination, but of different qualities of the original iron 196

ON THE

CHAPTER V.

MAGNETICAL POWERS OF STEEL PLATES OF

DIFFERENT MASSES, DENOMINATIONS, AND QUALITIES,

AND MEASURES OF COMBINATION, PREPARED FOR

THE NEEDLES OF SEA-COMPASSES, WITH THE EFFECT
OF SPACING THE PLATES.

202

Sect. I.-Experiments with Plates for Compass-Needles of best

cast-steel, tempered equally throughout, at a spring temper 204

Sect. II.-Experiments with Plates for Compass-Needles, of

superior qualities of steel of various kinds and denominations,

made quite hard

ON

2. Experiments with five series of 7.5 inch Compass-

Needles, of 0.75 inch in breadth

1. Experiments with five series of 6-inch Compass-Plates,

being 0.56 inch broad

CHAPTER VI.

THE EFFECTS OF THE ANNEALING OF HARD

STEEL PLATES OF DIFFERENT KINDS AND MASSES,

ON THEIR MAGNETICAL PROPERTIES, BOTH SINGLY

AND IN PAIRS

Sect. I.-On the Effects of annealing Hard Steel Plates in

boiling linseed Oil

-

Sect. II. On the Effects of annealing on hard Steel Plates, in

hot Oil, at various degrees of temperature

Sect. III.-On the Effects of annealing, at various Temperatures,

on the Magnetic Powers of hard Steel Bars, single and com-

pound, of the Horse-shoe form

RESULTS

ON THE

PAGE

228

235

250

§ I. Results in respect to difference of Denomination in the

same quality of hard Steel

§ II. Results in respect to difference of Quality in the same

denomination of hard Steel

§ III. Results as to the Changes in Magnetic Properties

produced in hard Steel of different denominations and

qualities by annealing in boiling linseed Oil

254

258

- 260

IV. Effects of annealing on the Energy of hard straight-

bar or plate Magnets, at degrees of temperature inferior

to that of boiling Oil

-

V. Results on the Magnetical Capacities and Powers of

Steel Plates, or Bars, adapted for Sea-Compasses, both

single and compound, whether hard, or whether

annealed at various temperatures, with the Effects of

spacing the Plates

§ VI. Results in respect to the peculiar Effects of hardness

and annealing on Magnets of the Horse-shoe form

CHAPTER VII.

INVESTIGATION

-

283

POWERS OF HARD STEEL BARS COMBINED IN

VARIOUS WAYS, AS ALSO IN PROPORTIONAL MASSES,

So AS TO FORM COMPOUND MAGNETS OF LARGE

DIMENSIONS AND OF GREATER LENGTHS THAN THOSE

OF THE ORIGINAL ELEMENTARY BARS; WITH A

PRELIMINARY

CONCERNING THE

METHODS OF DETERMINING THE RELATIVE POWERS

OF MAGNETS OF DIFFERENT LENGTHS.

Case I. Comparison of the Powers of various Bar-magnets

of the same length (viz. six inches), as determined by the

methods of Torsion and of Deviations, in order to the further

verification of the method of Deviations

289

Case II.-The Determination, experimentally, in Magnets of

different lengths, of the relation of their respective deviating

effects (at distances from the Compass proportional to their

several lengths) to their actual directive powers

Case III. The comparative Capacities for Magnetism of equi-

valent, or similarly proportioned, Bars of Steel of different

lengths, as Determined both by the method of Deviations and

that of Torsion

Sect. I. As to the proportional Powers of Magnets of different

lengths, but in all other respects, both as to dimensions in

breadth and thickness, and in quality and hardness of Steel,

the same

292

295

310