PREFACE. xv 



to works of practical utility. All other early efforts 

 were purely elementary or experimental. 



Let us take an illustration from another branch of 

 science. It is not unreasonable to suppose that Elec 

 tricity, using the term in its most extended sense, will 

 some day or other supersede steam. We probably only 

 require to be able to collect it cheaply and to control 

 it effectually, to employ the artillery of heaven on the 

 wide ocean, on our network of iron rails, and through 

 out all our manufacturing establishments. A, we will 

 suppose, invents the first efficient Electric Engine, which 

 with fifty horse power is fully at work ; and in the 

 course of a few years we sit down to write the history 

 of this engine invented by A. Where shall we start 

 in our history ? Did not Faraday years ago produce an 

 electro-magnetic engine ; then of course Faraday in 

 vented A. s engine ! But we need not stop here ; we 

 have the whole history of electricity before us. There 

 is no end of machines and engines ; and a patent speci 

 fication may come to light, the nearest possible thing 

 to A. But we have not done yet, we have to consider 

 France, &c., where we may find some more elemen 

 tary electrical models before Faraday, and then of 

 course before A. So that, on this system, as hitherto 

 adopted, in attempting to settle a claim for De Caus, 

 and depreciating the claim of the Marquis of Worcester, 

 we may venture to predict an analogous fate for the 

 Electric Engine, hereafter to be invented by some 

 inventor, A. Here we must plainly see that all that 

 has hitherto been invented in this electrical line, does 

 not go beyond model or elementary apparatus, and that 

 however nearly some of these may approach any plan 

 hereafter to be invented, it would be ridiculous and 

 highly reprehensible to set up claims based on no prac 

 tical value, and only colourably similar in some single 

 particular, but otherwise of no greater concern than as 



