CONTENTS. Sect. I. Of the relative Powers of Combinations of Magnetized RESULTS 1. As to hard Plates - 2. As to hard Bars in combination Sect. II. Of the Magnetical Powers, separately, and in combi- 153 Sect. III. Of the Magnetic Powers of Combinations of very hard ON THE - - PAGE CHAPTER IV. ON THE RELATIVE POWERS, IN COMBINATION AND SEPA- - 185 . 189 1 Experiments with Steel of different denominations, 159 - 168 175 - 133 € 195 2. Experiments with Steel of different denominations, · 189 1. Experiments with five series of 6-inch Compass-plates, CHAPTER V. MAGNETICAL POWERS OF STEEL PLATES OF Sect. I.-Experiments with Plates for Compass-needles of best · 208 2. Experiments with five series of 7.5 inch Co pass- 196 202 209 210 STEEL PLATES OF DIFFERENT KIN D AND MASSES, ON THEIR MAGNETICAL PROPERTIES, BOTH SINGLY Sect. II. On the Effects of annealing on hard Steel Plates, in Sect. III.-On the Effects of annealing, at various Temperatures, § IV. Effects of annealing on the Energy of hard straight- III. Results as to the Changes in Magnetic Properties produced in hard Steel of different denominations and § 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 § VI. Results in respect to the peculiar Effects of hardness 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 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 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 Case III. The comparative Capacities for Magnetism of equi- valent, or similarly proportioned, Bars of Steel of different 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, OF THE MAGNETICAL POWERS, RECEPTIVE AND PERMA- NENT, OF CAST IRON, BOTH IN SEPARATE BARS Sect. II.-As to the proportional Powers of Magnets combined as in the figures (plate iv.), compared with those in a single Sect. III. As to the relation of the Powers of Bars of twelve and of those of eighteen inches when combined so as to con- stitute masses of the same form, dimensions, and weight Sect. IV. As to the relative Powers of Combinations of twelve or eighteen inch bars, each kind by itself, and those of equal masses and dimensions composed of the two kinds, intermixed 316 Sect. V. As to the relative Powers of various Combinations of Bars of the same description (except as to the length of the integrant bars) in proportional masses Sect. VI.-As to the extent to which small Magnets, made quite hard, may be advantageously combined, with a view to the formation of larger artificial Magnets than have yet been MAGNETICAL INVESTIGATIONS. PART II. INVESTIGATIONS CONCERNING THE LAWS OR PRINCIPLES AFFECTING THE POWER OF MAGNETIC STEEL PLATES OR BARS IN COMBINATION. CHAPTER I. AS TO THE POWERS OF COMBINATIONS OF MAGNETISED PLATES OF TEMPERED STEEL, IN CONTACT. THIS important object of inquiry-as affecting both the directive power of compass needles and the energy of compound magnets--has been pursued to a much greater extent, and with a much larger variety and assortment of plates and bars, than it may here be necessary, or indeed useful, to describe. In the whole, the powers in combination of about forty sets of plates or bars, have been carefully tried, in their respective series of from 2 to 192 together, -the total amount of magnetised pieces of steel, subjected to experiment, being scarcely less than from seven to eight hundred. And in several of the sets of bars or plates, the powers in combination were likewise H |