88 Mr. MuUins's Observations on an improved Construction 



series of experiments I adopted and recommended in pre- 

 ference. In making these remarks I am quite sure that the 

 readers of the Philosophical Magazine will do me the justice 

 to believe that I am actuated by no other motive than a sin- 

 cere and honest desire to place in their hands an instrument 

 of research as powerful and as perfect as my investigations 

 enabled me to make it, in place of one which, although as 

 much my arrangement as that subsequently adopted by 

 me, did not certainly afford equally satisfactory results. It is 

 quite clear that the first mode of construction being as much 

 mine as the second, there was no reason why I should have 

 preferred the latter, if I had not clearly ascertained that it 

 was superior to the former ; and under such circumstances, the 

 discoveries recently made in the development and applications 

 of metallic electricity being so important, and so certain to 

 lead to extraordinary as well as beneficial results, it becomes 

 my duty, and 1 will add, the duty of every true lover of science, 

 to endeavour to put into the hands of his fellow-labourers, 

 who may not have equal opportunities with himself of ascer- 

 taining their relative merits, those instruments of research 

 which laborious investigation may have proved to him to be 

 best suited to the purposes of further discovery. 



With these preparatory remarks, which go to show how my 

 sustaining battery was at first arranged, and subsequently 

 improved by me some three years since, I now proceed to 

 the proper subject of this paper, namely, the description of a 

 further improvement, not only in the mode of construction, 

 but also in what may be properly termed the necessary con- 

 stituents of the sustaining battery. 



Although the introduction of a membranous partition be- 

 tween the zinc and copper surfaces was productive of great 

 advantages, the chief of which was the obtainment of undi- 

 minished power for a long period, I soon perceived that the 

 battery was still far from perfect, and that the remedy for one 

 defect unfortunately created another. It was true that the de- 

 posit of injurious elements upon either metallic surface, or upon 

 both, was prevented by the interposition of membrane ; but 

 it so happened, that after a few hours' action pure copper was 

 not only precipitated upon the external surface of the copper 

 cylinder, where alone it should have been attracted, but it was 

 also deposited upon the surface of the membrane, and actually 

 formed within its substance, and on the surface next the zinc, 

 thereby creating local action, with its consequence, gi'eat 

 waste of zinc, and tending to diminish the general effect. This 

 was a source of great annoyance where it was desirable to 

 keep up the action for a long period ; for not only the copper 



