NATURAL PHILOSOPHY. 109 



may not have arrived at the best form of voltaic battery, yet that we 

 had learned sufficiently of the law of electro-magnetic forces to declare 

 that, under any conditions, the amount of magnetic power would de- 

 pend on the change of state, consumption of an element, in the bat- 

 tery, and that the question resolved itself into this : What amount 

 of magnetic power can be obtained from an equivalent of any material 

 consumed? The following were regarded as the most satisfactory 

 results yet obtained: 1. The force of the voltaic current being 

 equal to 678, the number of grains of zinc destroyed per hour was 

 151, which raised 9,000 pounds one foot high in that time. 2. The 

 force of current being, relatively, 1,300, the zinc destroyed in an hour 

 was 291 grains, which raised 10,030 pounds through the space of one 

 foot. 3. The force being 1,000, the zinc consumed was 223 grains; 

 the weight lifted one foot 12,672 pounds. One grain of coal consumed 

 in the furnace of a Cornish engine lifted 143 pounds one foot high, 

 whereas one grain of zinc consumed in the battery lifted only 80 

 pounds. The cost of one hundred-weight of coal is under 9d. ; the 

 cost of one hundred-weight of zinc is above 2lQd. Therefore, under 

 the most perfect conditions, magnetic power must be nearly twenty- 

 five times more expensive than steam-power. But it is an impossibil- 

 ity to reach even this, owing, in the first place, to the rate with which 

 the force diminishes through space. As the mean of a great many 

 experiments on a great variety of magnets, of different forms and 

 modes of construction, the following result was given : Magnet and 

 armature in contact, lifting force 220 Ibs. ; magnet and armature dis- 

 tant one 250th of an inch, 90. 6 Ibs. ; distant one 125th of an inch, 

 50. 7 Ibs. ; distant one 63d of an inch, 50. libs. ; distant one 50th of an 

 inch, 40. 5 Ibs. Thus, at one 50th of an inch distance, four fifths of the 

 power is lost. This great reduction of power takes place when the 

 magnets are stationary, but a greater reduction of original power is 

 occasioned when they are set in motion. Indeed, any disturbance pro- 

 duced near the poles of a magnet diminished its attractive force dur- 

 ing the continuance of the motion. The attractive force of a magnet 

 being 150 pounds when free of disturbance, it fell to one half by 

 causing an armature to revolve near its poles. Therefore, when a 

 system of magnets constructed to produce a given power is set in rev- 

 olution, every magnet at once suffers an immense loss of power, and 

 consequently their combined action falls in practice very far short of 

 their estimated power ; this fact has been before distinctly stated. 

 And not merely does each magnet thus sustain an actual loss of power, 

 but the power thus lost is converted into anew form offeree, or rather 

 becomes a current of electricity, acting in opposition to the primary 

 current by which the magnetism is induced. From an examination 

 of all these results, Mr. Hunt is disposed to regard electro-magnetic 

 power as impracticable, on account of its cost, which must necessarily 

 be, he conceives, under the best conditions, fifty times more expensive 

 than steam-power, and is at present at least one hundred and fifty times 

 as expensive. London Athen&um, June. 



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