Mr. Watkins oft Eledro-mametic motive Machines. 193 



•b 



figure, but it has a contrivance of points dipping successively 

 into the mercury in a divided wooden cup. One partition of 

 the cup is connected with one element of the battery, while 

 the other partition is in communication with the other element 

 of the battery. The communicating wires from the division in 

 the cup proceed down the hollow wooden column to the coil 

 of wires surrounding the soft iron, while the battery wires pro- 

 ceed up the column, but not in contact, and finish by being 

 connected to two separate cups with mercury, in which revolve 

 two small circular discs of platinum affixed to the axis, one on 

 each side of the divided cup, and supported by two wood arms 

 from the top of the column. The dipping points are so in- 

 sulated and arranged on the axis that they reverse the direction 

 of the current in the wire coils, and so effect the order of po- 

 larity in the soft iron magnet : this being accomplished at the 

 right period the motion of the permanent steel magnets is 

 obtained. 



Two pullies are attached to the axis, bands from which will 

 urge trifling pieces of machinery. 



I have constructed a more simple form of motive machine 

 than that of fig. 2. Plate IV. It has only one electro-magnet 

 and two permanent steel magnets. The axis or shaft is of the 

 same description as that with the four magnets : it works re- 

 markably well, and the axis having only to carry one system 

 of magnetic arms revolves with great velocity, and raises nearly 

 an equal ^weight in the same time and distance as that with the 

 four magnets. 



The batteries I employ for obtaining the electrical currents 

 are small, and constructed upon the plan proposed by Pro- 

 fessor Daniells, King's College, London, and called by him the 

 constant battery. This plan of the battery I consider to be 

 original and the best devised for constant action and conveni- 

 ence of manipulation. 



When we reflect that magnetic attractive force is the funda- 

 mental principle upon which the motive machines act, the 

 limited space through which this force operates to a working 

 amount, and our imperfect means of developing its powers, it 

 may be excusable if we pause before giving in the present state 

 of our knowledge an unreserved assent to the ultimate success 

 of employing its agency as a prime mover on an extensive 

 scale. 



I have mentioned that many trifling machines or philoso- 

 phical toys, in addition to those I have just now described, 

 have been constructed, and plenty more, I have no doubt, will 

 be brought forward and work very successfully ; and when 

 they operate by continued rotatory motion of the shaft, carry- 



PMLMag. 6'. 3. Vol. 12. No. 73. Feb. 1838. Z 



