Things not generally Known. 



England in the year 1829, were united by a jointed cartilagi- 

 nous band. A silver tea spoon being placed on the tongue of 

 one of the twins and a disc of zinc on the tongue of the other, 

 the moment the two metals were brought into contact both 

 the boys exclaimed, " Sour, sour ;" thus proving that the gal- 

 vanic influence passed from the one to the other through the 

 connecting band. 



MINUTE AND VAST BATTERIES. 



Dr. Wollaston made a simple apparatus out of a silver thim- 

 ble, with its top cut off. It was then partially flattened, and 

 a small plate of zinc being introduced into it, the apparatus was 

 immersed in a weak solution of sulphuric acid. With this mi- 

 nute battery, Dr. Wollaston was able to fuse a wire of platinum 

 fto'ooth of an inch in diameter a degree of tenuity to which no 

 one had ever succeeded in drawing it. 



Upon the same principle (that of introducing a plate of zinc 

 between two plates of other metals) Mr. Children constructed 

 his immense battery, the zinc plates of which measured six feet 

 by two feet eight inches ; each plate of zinc being placed be- 

 tween two of copper, and each triad of plates being enclosed in 

 a separate cell. With this powerful apparatus a wire of plati- 

 num, Voth of an inch in diameter and upwards of five feet long, 

 was raised to a red heat, visible even in the broad glare of day- 

 light. 



The great battery at the Royal Institution, with which Sir 

 Humphry Davy discovered the composition of the fixed alkalies, 

 was of immense power. It consisted of 200 separate parts, each 

 composed of ten double plates, and each plate containing thirty- 

 two square inches ; the number of double plates being 2000, and 

 the whole surface 128,000 square inches. 



Mr. Highton, C.E., has made a battery which exposes a sur- 

 face of only T-j^yth part of an inch : it consists of but one cell ; it 

 is less than 10 oooth part of a cubic inch, and yet it produces 

 electricity more than enough to overcome all the resistance in 

 the inventor's brother's patent Gold-leaf Telegraph, and works 

 the same powerfully. It is, in short, a battery which, although 

 it will go through the ei/e of a needle, will yet work a telegraph 

 well. Mr. Highton had previously constructed a battery in size 

 less than -^th of a cubic inch : this battery, he found, would 

 for a month together ring a telegraph-bell ten miles off. 



ELECTRIC INCANDESCENCE OF CHARCOAL POINTS. 



The most splendid phenomenon of this kind is the combus- 

 tion of charcoal points. Pointed pieces of the residuum ob- 

 tained from gas retorts will answer best, or Bunsen's composi- 

 tion may be used for this purpose. Put two such charcoal 



