I 



ADDRESS. 1 3 



■where the motive power is derived from a water-wheel. The dynamo 

 machine there employed was exhibited at the Paris Electrical Exhibition 

 by Dr. Werner Siemens, its peculiar feature being that the conductors 

 upon the rotating armature consisted of solid bars of copper 30 mm. 

 square, in section, which were found only just sufficient to transmit the 

 large quantity of electricity of low tension necessary for this operation. 

 One such machine consuming 4-horse power deposits about 300 kilo- 

 grammes of copper per 24 hours. 



Electric energy may also be employed for heating purposes, but in 

 this case it would obviously be impossible for it to compete in point of 

 economy with the direct combustion of fuel for the attainment of ordinary 

 degrees of heat. Bunsen and St. Claire De Ville have taught us, how- 

 ever, that combustion becomes extremely sluggish when a temperature of 

 1,800° C. has been reached, and for effects at temperatures exceeding that 

 limit the electric furnace will pi'obably find advantageous applications. 

 Its specific advantage consists in being apparently unlimited in the degree 

 of heat attainable, thus opening out a new field of investigation to the 

 chemist and metallurgist. Tungsten has been melted in such a furnace, 

 and 8 pounds of platinum have been reduced from the cold to the liquid 

 condition in 20 minutes. 



The largest and most extensive application of electric energy at the 

 present time is to lighting, but, considering how much has of late been 

 said and written for and against this new illuminant, I shall here 

 confine myself to a few general remarks. Joule has shown that if an 

 electric current is passed through a conductor the whole of the energy 

 lost by the current is converted into heat; or, if the resistance be 

 localised, into radiant energy, comprising heat, light, and actinic rays. 

 Neither the low heat rays nor the ultra-violet of highest refrangibility 

 affect the retina, and may be regarded as lost energy, the effective rays 

 being those between the red and violet of the spectrum, which in their 

 combination produce the effect of white light. 



Regarding the proportion of luminous to non-luminous rays proceeding 

 from an electric arc or incandescent wire, we have a most, valuable 

 investigation by Dr. Tyndall, recorded in his work on ' Radiant Heat.' 

 Dr. Tyndall shows that the luminous rays from a platinum wire heated 

 to its highest point of incandescence, which may be taken at 1,700° C, 

 formed oV^h part of the total radiant energy emitted, and ^^V^^ P^^^ i^ 

 the case of an arc light worked by a battery of 60 Grove's elements. 

 In order to apply these valuable data to the case of electric lighting 

 by means of dynamo currents, it is necessary in the first place to deter- 

 mine what is the power of 50 Grove's elements of the size iised by 

 Dr. Tyndall, expressed in the practical scale of units as now established. 

 From a few experiments lately undertaken for myself, it would appear 

 that .50 such cells have an electro-motive force of 98-5 Volts, and an 

 internal resistance of 13'5 Ohms, giving a current of 7"o Amperes when 

 the cells are short-circuited. The resistance of a regulator such as Dr. 



