1 50 Proceedings. 



the use of the Hme-Hght, or Drummond h'ght, as it was then 

 called, made such application possible. The exhibition of 

 photography on so colossal a scale took the world by 

 surprise, and this grand application of the marvellous art, 

 which has now become so familiar, was received with the 

 admiration it deserved. Mr. Dancer's services to the lantern 

 did not end with the application of photography to it ; he 

 also improved the arrangement of the optical parts^ 

 producing a clearer image and a flatter field than had before 

 been obtained. At the Mechanics' Institution Exhibitions 

 Mr. Dancer was in no small measure responsible for the 

 '' fairy fountain," or, as it was first called, the " optical chro- 

 matic fountain." The fairy fountain of the Jubilee Exhition 

 of 1887 was an extension of the original idea, and though' 

 shown on a much grander scale and in the open air, did not 

 excel the beauty of the original Mechanics' Institution 

 fountain. 



A complete list of the instruments, apparatus, and 

 processes in the invention or improvement of which Mr. 

 Dancer was concerned is too considerable to reproduce 

 here. In 1838 he suggested the introduction of earthenware 

 porous jars to separate the two solutions used in voltaic 

 batteries, which before this time was effected by means of 

 bladder or other animal tissue. Porous jars have since been 

 universally used. Dr. Golding Bird, in his " Elements of 

 Natural Philosophy," published in 1839, gave Mr. Dancer 

 credit for the invention of the porous jar ; but that is the 

 most conspicuous acknowledgment he received for an 

 improvement of the very greatest importance to science. 

 In the same year he invented a still more important 

 instrument, namely, the automatic contact breaker, or the 

 vibrating interrupter — an instrument of universal application 

 at the present day wherever electricity is employed for 

 telegraphy or signalling. Again, in 1838, and resulting 

 from the same experiments, came the deposition of metallic 



