:26 



NATURE 



{Jan. 31, 1884 



Second Pos'Ickh'I 10 I'art IV. "Phil. Tka.ns.,'' I'Ara' II., 

 \'ui.. ci.xxiv. 

 Striking Dislaiia: — In a 1 ost-ciipt to Part IV. of our re- 

 searches,' we .stated that, with 14,400 cells, partly of the rod 

 form, partly of the chloridein-|)i>\vder form, the length of the 

 spark between paraboloidal points was 07 inch (i7'8mm.), 

 and bet'ieen a point .and di,k 0'62 inch (I5'7 mm.), and that 

 it does not appear, therefore, that the law of the spark beini; a^ 

 the square of the number of cells lulds good beyond a certain 

 nu-nber. 



These results were obtained at the Royal Institution ; since 

 the removal of the battery to our laboratory we had not, at the 

 date of the poitscript to Part IV. of our researches, charged up 

 the "hole of it. Recently, however, \\e have put the battery in 

 thorough order, by scraping the zinc rods ' of the cells already 

 charged up and added newly made up cells to liring up the total 

 to 15,000 cells, all of the rod form. 



Having ih' whole 15,000 cells in perfect order, we thought 

 th.ot it would be desirable to make fresh determinations of the 

 striking distance, increasing the potential a thousand cells at a 



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161111 



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ti lie, leSween two very slightly conve.x disks (plane.-.), a point 

 ;iiid disk, and two paraboloidal points. These points are one- 

 eight'a of an inch (3'I75 mm.) in diameter, and three-ei^hlhs 

 ot an inch (9'525 mm.) long. In the case of a point and 

 .li-k, the point was like one of those used for two points, and 

 lOe di-k was i/,, inch [3'334 cm.] in diameter. The two 

 I lanes used were i^"^ inch [3'334 cm.] in diameter. 



As the points, particularly tlie negative, are deformed by the 

 discharge, the precaution was taken to touch up the point afier 

 each discharge in the shaping-tool, scre.ved to the mandril of the 



' Phil. T,a 



vol. cK 



lathe, mentioned in Part I. of our researches,"- and thus to 

 restore them to a true paraboloidal form. 



Results were obtained which are plotted down in the diagram. 



The several results, the different sets being distinguished by 

 plain crosses or crosses with a dot, are laid down on the diagram, 

 Fig. I, to which are aUo added other results already published 

 froai former experiments ; these latter have a ring on one of the 

 members of the cross. 



fixychlor'ide of ui 



lavei -sf p.-ir-i'Tin t 



- I'hil. T.ant.. 



naking experiments in order to prevent the depo 

 he z.nc rods by covering the charging fluid w 



- p. 75, separate copy p. 25. 



