288 
POPULAR SCIENCE REVIEW. 
A valuable suggestion has been made by Mr. Tisley for eoiling 
the armature rotating within an electro-magnet with two 
distinct wires so arranged that the terminals of one being in 
connection with the electro-magnet supplies a current to charge 
it whilst a current is carried off by the other wire to do the 
practical work required of the machine. 
The machine in the Paris Exhibition has two armatures 
measuring 12 in. long 2^ in. diameter; when arranged for 
quantity, it will give 250 cubic centimetres of mixed gases 
per minute. It has melted 18 in. of platinum wire 1 millimetre 
thick, and will maintain 4 feet 6 inches of wire 0*01 diameter 
persistently at white heat. 
In these machines the conversion of the dynamical or driving 
power is direct and seemingly suffers comparatively but very 
little loss, and this feature is well shown in the sensitive fluctua- 
tions of the incandescence of the platinum wire between the 
terminals in consonance with the variations of the speed. 
The final success amongst all these various and future plans 
will be in favour of that which will yield the most economic 
utilization of the primary dynamical power, and that will do this 
without inconvenience or delay from the swelling of the arma- 
tures, heated by the magnetic friction when rapidly rotated. 
The charge sent into the electro-magnet must almost be con- 
trolled within proper proportions, otherwise there will be a gain 
of resistance that will accumulate in the machine until it 
equals or overcomes the motive power. Something has been 
already done in this last direction by the magnetic shutter, pro- 
posed by Mr. Tisley and which being proportionately slid over 
the ends of the plates ( k 1c) partially cuts off the magnetism 
acting upon the generating armature, at the same time that it 
gives improved effect in the armature for external work by 
completing the horse-shoe form of the magnet. In this way 
the power to work it can be regulated from two men to two 
horses, the total result produced of course depending upon the 
power primarily applied. These practical electrical subjects 
are already deeply occupying men’s minds, and their pursuit 
must bring forth good fruit. In a few years, perhaps sooner, 
it will be our duty again to come forward to describe other new 
electrical machines. 
