40 Mr. MuUins 07i the Voltaic Battery. 



joinings being closed without solder, at least externally ; the 

 inside is filled with fine dry sand to the height of 4,1 inches, 

 for the purpose of keeping the cylinder steady, and upon the 

 sand is placed a copper shelf soldered to the inner surface of 

 the cylinder; this shelf is meant to hold crystals of sulphate 

 of copper and communicates with the external surface of the 

 cylinder by means of a number of holes about ^ths of an 

 inch apart, made in the circumference and on a level with 

 the shelf; by this arrangement there is a constant supply of 

 the salt of copper in solution to the fluid which lodges be- 

 tween the external surface of the cylinder and the wooden 

 partition in which it stands ; whereas, in the case of the open 

 cylinders, one of their greatest defects wiis, that the crystals, as 

 they were dissolved, were mixed with the internal solution 

 where they were not wanted (there being no zinc surface op- 

 posed) in place of the exteriial, where they Were ; and thus, 

 not only was the solution unequal in strength, but it was 

 weakest in the very part where all the action existed, namely, 

 between the opposed surfaces of zinc and copper. The copper 

 cylinder stands in a wooden cylinder made of seasoned syca- 

 more, or other white wood, and wide enough to allow the 

 copper vessel to pass into it with perfect freedom ; the bottom 

 of this cylinder is ^th of an inch thick coated over with some 

 non-conducting substance ; the cylindrical part not more 

 than ypth, and it can be made without any difficulty by an}' 

 handy turner. Its height is less than that of the copper by 

 ^th of an inch, and both are surrounded by an open cylinder 

 of zinc {not less than \th of the height of the copjjer) im- 

 mersed in a solution consisting of equal parts of the saturated 

 solution of muriate of ammonia and of water. The sulphate 

 solution stands sufficiently high in the copper cylinder to 

 admit of its passing through the holes round the shelf; but 

 not higher. The entire arrangement is placed in a glazed 

 earthenware pot, resting on a stand in which two glass cups 

 are fixed for mercury. This is unquestionably one of the sim- 

 plest and cheapest forms of battery ever constructed. Of its 

 power or utility I will only say that it satisfies me, and that if 

 those who want such instruments will only judge for themselves^ 

 I am quite confident of its satisfying any impartial inquirer. 



For intensity effects I use a compound battery of ten, in 

 which each cylinder is only 3| inches high and 2 in diame- 

 ter, the other parts being in proportion and the mode of ar- 

 rangement being similar * : and for increased quantity effects 



* Both batteries may be seen in action at theAdelaide Gallery of Science, 

 as well as those upon my original plan. 



