Intellisence and Miscellaneous Articles. 551 



•to 



of the law of electro-magnetic forces to declare, that, under any 

 conditions, the amount of magnetic power would depend on the 

 change of state, consumption of an element, in the battery, 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 ob- 

 tained : — 1. The force of voltaic current being equal to 678, the 

 number of grains of zinc destroyed per hour was 151, which raised 

 9000 lbs. 1 foot high in that time. 2. The force of current being 

 relatively 1300, the zinc destroyed in an hour was 291 grs., which 

 raised 10"030 lbs. through the space of 1 foot. 3. The force being 

 1000, the zinc consumed was 223 grs., the weight lifted 1 foot 

 12.672 lbs. 



The estimations made by Messrs. Scoresby and Joule, and the 

 results obtained by OErsted, and more recently by Mr. Hunt, very 

 nearly agree ; and it was stated that 1 gr. of coal consumed in the 

 furnace of a Cornish engine, lifted 143 lbs. 1 foot high, whereas 

 1 gr. of zinc consumed in the battery lifted only 80 lbs. The cost 

 of 1 cwt. of coal is under 9 pence, the cost of 1 cwt. of zinc is 

 above 216 pence. Therefore, under the most perfect conditions, 

 magnetic power must be nearly 25 times more expensive than steam 

 power. But the author proceeded to show that it was almost proved 

 to be an impossibility ever to reach even this condition, 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 large variety 

 of magnets, of different forms and modes of construction, the fol- 

 lowing results were given : — 



The magnet and armature being in contact, the lifting force 



was 220 pounds. 



distant -s-rTT of an inch 906 ... 



50-7 

 50-1 

 40-5 



1 

 ••• ^ so 



Thus at one-fiftieth of an inch distance four-fifths of the power 



are lost. This great reduction of power takes place when the mag- 

 nets are stationary. The author then proceeded to show that the 

 moment they were set in motion a great reduction of the original 

 power immediately took place ; that, indeed, any disturbance pro- 

 duced near the poles of a magnet diminished, during the continuance 

 of the motion, its attractive force ; the attractive force of a magnet 

 being 150 lbs. when free of disturbance, fell to one-half by occa- 

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

 system of magnets which had been constructed to produce a given 

 power is set in revolution, every magnet at once suffers an immense 

 loss of power, and consequently their combined action falls in prac- 

 tice very far short of their estimated power. This fact has not been 

 before distinctly stated, although the author is informed that Jacobi 

 observed it. And not merely does each magnet thus sustain an ac- 

 tual loss of power, but the power thus lost is converted into a new 



