This book is in no sense an exhaustive Life of Edison, and, indeed, could not be, seeing that the inventor is still young in heart and enthusiasm, and that there are probably many years of his brilliant career still to run. His grandfather and great grand father lived to be centenarians, and their noted descendant gives every indication of coming into healthy competition with them in the matter of a long life. And although Mr. Edison avers that he has quit the inventing business and is now de voting himself almost exclusively to pure science, there is every reason to hope that by his investiga tions many scientific problems will yet be solved, and that some of the secrets which Nature still holds will be revealed through him.