662 GROVE'S ELEMENTS. 



with one another. This is effected by using a thin 

 cylindrical vessel made of unglazed earthenware; the 

 vessel has only been slightly heated in the oven during 

 the process of manufacture, and has- there fore preserved 

 the porosity of the material. This i porous vessel,' 

 which contains one of the liquids, is placed inside a 

 second vessel of glass or glazed stoneware, which 

 contains the other liquid. The two liquids thus enter 

 the pores on opposite sides of the porous vessel, and 

 come into contact without seijsibly intermixing. The 

 zinc stands in both kinds of elements in dilute sulphuric 

 acid ; the carbon or platinum in concentrated nitric acid. 



The mode of action of these elements will be explained farther on. 

 The following directions are, in the meantime, intended to enable 

 the student to use the elements for the experiments on various 

 effects of the galvanic current. There are great differences in the 

 form, size, and mode of arrangement of the different parts of either 

 kind of element ; only one 'convenient construction of each kind 

 will, however, be described here. 



In fig. 339, A represents the exterior, and _Z? a section of a Grove's 

 element or ' cell.' In both figures gg is a glass vessel with stout 

 walls, 1 1 the porous clay cell, z z a hollow cylinder of zinc, which has 

 either been cast in a suitable mould or bent into the requisite shape 

 out of a sheet of stout zinc ; a short projection a serves for attaching 

 a binding screw to it. Within the porous cell is a sheet of platinum 

 fo\l,p, fixed to a cover of ebonite, h, which rests on the porous vessel. 

 The cover has a slit through which the platinum passes ; by the side 

 of the slit the cover bears a small vertical plate to which the top of 

 the platinum strip may be clamped. When only one element is to 

 be used, binding screws of the form shown in A and J5 are attached 

 to the zinc and platinum ; they are provided with holes for inserting 

 terminal wires, and also with pressure screws for clamping the 

 wires ; but if several elements are united to a battery, binding 

 screws of this kind are only used for the zinc in the last cell and 

 the platinum in the first, while the intermediate connection of the 

 elements is made by means of strips of sheet copper, which are 

 clamped to the metals by more simple binding screws. Fig. 339, (7, 

 shows in section the parts thus connected. D is a view of the 



