Without an over-large stock of expensive apparatus it is not easy for all boys in a class to do the same experiment at one lesson: nor is it necessary, for most boys now know something in a general way about electricity and in selecting experiments for them to perform I do not feel it necessary to adhere so closely to a logical order as I should were they on entirely new ground. I would suggest however to others who may use this book that at first the lessons should be largely demonstrations: later individual laboratory work may predominate, boys repeating for themselves experiments shewn previously in the theatre by their master.