Ir THE PROGRESS OF SCIENCE 109 



second in practical importance to the electric tele- 

 graph. Invented, as it were, only the other day, 

 it has already taken its place as an appliance of 

 daily life. ' Sixty years ago, the extraction of 

 metals from their solutions, by the electric current, 

 was simply a highly interesting scientific fact. At 

 the present day, the galvano-plastic art is a great 

 industry ; and, in combination with photography, 

 promises to be of endless service in the arts. 

 Electric lighting is another great gift of science to 

 civilisation, the practical effects of which have not 

 yet been fully developed, largely on account of its 

 cost. But those whose memories go back to the 

 tinder-box period, and recollect the cost of the 

 first lucifer matches, will not despair of the results 

 of the application of science and ingenuity to the 

 cheap production of anything for which there is a 

 large demand. 



The influence of the progress of electrical know- 

 ledge and invention upon that of investigation in 

 other fields of science is highly remarkable. The 

 combination of electrical with mechanical con- 

 trivances has produced instruments by which, not 

 only may extremely small intervals of time be ex- 

 actly measured, but the varying rapidity of move- 

 ments, which take place in such intervals and 

 appear to the ordinary sense instantaneous, is 

 recorded. The duration of the winking of an eye 

 is a proverbial expression for an instantaneous 

 action ; but, by the help of the revolving cylinder 



