2 10 Intelligence and Miscellaneous Articles. 



which in the daily differences belongs to our planet from that which 

 belongs to the sun itself ; but the principal results given here could 

 not be essentially modified. They show how imperfect is our know- 

 ledge on the absorption of terrestrial atmosphere, and on the abso- 

 lute force of solar radiation. — Comptes Rendus, January 4, lb 64. 



ON THE ELECTRICAL PROPERTIES OF PYROXYLINE -PAPER AND 

 GUN-COTTON. 



Prof. John Johnston, of Wesleyan University, Ct., has called my 

 attention to a remarkable power in pyroxyline-paper of producing 

 positive electrical excitement in sulphur, sealing-wax, &c. His note 

 is as follows : — 



<c Weslevan University, Middletovvn, 

 * December 24, 1863. 



"Dear Sir, — We are told by writers on electricity that sulphur 

 by friction with all other substances becomes negatively excited ; as 

 cat's fur, on the other extreme, by friction with all other substances 

 becomes excited positively. But a few days ago I made the disco- 

 very that sulphur by friction with paper pyroxyline (I will call it) 

 is excited w r ith positive electricity, as are also sealing-wax, amber, 

 &c. The paper is prepared in the same manner as gun-cotton, which 

 would also in all probability be found to possess the same property. 



" Enclosed you w T ill find some of the paper for trial. It was pre- 

 pared by my son, M. M. Johnston. 



" Perhaps you will think the matter of sufficient importance to 

 make a note of it in the Journal of Science. 



" Respectfully yours, 



" Prof. Silliman." " John Johnston." 



I have repeated and confirmed Prof. Johnston's experiment, extend- 

 ing it to gun-cotton. I find, as he suggests, that the latter substance 

 produces the same excitement of positive electricity which is pro- 

 duced by the pyroxyline-paper. The most energetic effects are 

 produced when vulcanized india-rubber is the electric. The oppo- 

 site effects in this substance produced by flannel and the gun-cotton 

 or pyroxyline-paper are very striking, and will form a good lecture- 

 room illustration. These substances also produce powerful positive 

 excitement in glass. It is difficult from the use of pith-balls alone 

 to determine which produces the most powerful positive excitement, 

 glass or hard rubber, when excited by gun-cotton or pyroxyline- 

 paper. This seeming anomaly, confounding our ordinary means 

 of discrimination in cases of electrical excitement, demands further 

 investigation. It would appear that of negative electrics yet observed 

 these azotized species of cellulose are the most remarkable — in com- 

 parison with which the most highly negative electrics hitherto known 

 become positive. — B. Silliman, Jun. — Silliman's American Journal, 

 January 1864. 



