296 Michael Faracly, Esq., on the 



stance for the excitement of negative electricity. It is hardly 

 possible to take one of the soles sold by the shoemakers out 

 of paper, or into the hand, without exciting it to such a de- 

 gree as to open the leaves of an electrometer one or more 

 inches ; or, if it be unclectrified, the slightest passage over 

 the hand or face, the clothes, or almost any other substance, 

 gives it an electric state. Some of the gutta percha is sold 

 in very thin sheets, resembling, in general appearance, oiled 

 silk ; and if a strip of this be drawn through the fingers, it 

 is so electric as to adhere to tlie hand, or attract pieces of 

 paper. The appearance is such as to suggest the making a 

 thicker sheet of the substance into a plate electrical machine 

 for the production of negative electricity. 



" Then as to inductive action through the substance, a sheet 

 of it is soon converted into an excellent electrophorus ; or it 

 may be coated, and used in place of a Leyden jar, or in any 

 of the many other forms of apparatus dependent on inductive 

 action. 



'- " I have said, that all gutta percha is not in this electrical 

 condition. AVith respect to that which is not so (and which 

 has constituted above one-half of that which, being obtained 

 at the shops, has passed through my hands), it has either 

 discharged an electrometer as a piece of paper or wood would 

 do, or it has made it collapse greatly by touching ; yet has, 

 on its removal, been followed by a full opening of the leaves 

 again. The latter effect I have been able to trace and refer 

 to a conducting portion within the mass, covered by a thin ex- 

 ternal non-conducting coat. When a piece which insulates 

 well is cut, the surface exposed has a resinous lustre and a 

 compact character that is very distinctive ; whilst that which 

 conducts has not the same degree of lustre, appears less 

 translucent, and has more the aspect of a turbid solution so- 

 lidified. I believe both moist steam-heat and water-baths 

 are used in its preparation for commerce ; and the difference 

 of specimens depends probably upon the manner in which 

 these are applied, and followed by the after-process of roll- 

 ing between hot cylinders. However, if a portion of that 

 which conducts be warmed in a current of hot air, as over 

 the glass of a low gas-flame, and be stretched, doubled up. 



