Microscopical Society
A meeting of the above society was held in the Grammar School, on Wednesday evening last, the Rev. W. R. Weston (Vice-President) in the chair.
Forty-eight members and friends were present
Mrs. Thomas. Turner, Miss C. Liddle, the Rev. G. Jennings, Mr. W.E. Shirley and Mr. Tretheway were elected members of the society.
Mr. Cuttriss then gave a lecture on “The Electric Light – What it is and how it is produced.”
Mr. Cuttriss first enumerated the various sources of electricity, and then gave a general description of the better known arc & incandescent system of illumination, including among the former the Jablochkoff and Brush lights, and among the latter Edison’s & Swan’s. The arc system is more especially applicable to large buildings & open spaces; the incandescent lamp being adapted for smaller rooms, such as would be met with in private houses.
The lecturer then exhibited and described a dynamo machine, now such an important factor in connection with electric lighting for, though galvanic batteries will answer on a small scale, it is to that machine that we must look for the future development of this new light. The dynamo machine is essentially an apparatus for the conversion of mechanical force and Electric Force. It is an instrument in which an armature is caused to rotate very rapidly between the poles of one or more electric (1) magnets , termed field magnets.
Starting with the residual magnetism and (2) the field magnets, the at first feeble current produced in the armature wires by the rapid culling (3) of the magnetic lines of force during rotation, is gradually intensified by the increasing magnetism generated in the field magnets through the circulation of the current round them. This accumulation goes on until the magnets are sufficiently charged, if then the speed of the machine be maintained at a regular rate a uniform current, insuring a steady light, results.
The intensity of the light, within certain limits, being proportional to the speed of the machine. By means of a hand dynamo machine, Swan Lamps of 5, 10 & 20 candle power, were exhibited in operation, and their mode of construction was also explained. The Swan Lamp consists of a glass globe of one and a half to two inches in diameter, exhausted of air in the most perfect manner known and hermetically sealed. Enclosed 4 within is a loop of carbon, formed by carbonising a piece of cotton thread by a special process; this loop is attached to two platinum wires passing through the lower part of the globe & forming a connection with the machine. When a current is passed through the wires from a battery, the resistance offered by the carbon thread (carbon being a bad conductor of electricity) causes it to become so intensely heated, and as there is no air present in the globe the carbon does not burn away as it would under ordinary conditions.
A good discussion followed during which a number of questions were put to and answered by the lecturer. A vote of thanks to Mr. Cuttriss was then proposed by the chairman and carried unanimously.
Notes
1. A correction was marked over the word ‘eletric’ changing it to ‘elctro’
2. A correction was marked over the word ‘and’ changing it to ‘of’
3. In the minute book the word ‘cutting’ is used instead of ‘culling’
4. The word ’Enclosed’ is scored out in the cutting
This paper was read at the ordinary meeting of 19 November 1882