504 



t>ItOl7UCTI0N dF EtECTRTCITY BY FttlCtitt^A 



white carrying' on his speculations concerning the nativt* 

 country of the potato, lies under the pressure of a favourite 

 theory, — in my opinion a very feeble one, — " that there is 

 not a singlv?faC", by which the liistory of South America is 

 connected with that of North America". I shall examine 

 The history of this theory in another place. I shall even endeavour to 

 show,' by an attention to different species of vegetables. 



■who i-: prcjii 

 dic-ii b,7 a i'i 

 ■vorite hypo- 

 thesis. 



■North and 

 South Ame- 



rica counec 

 by various 

 ■facts. 



ted which ivere unquestionably found in a cultivated state in this 

 two Americas, that there is not only a "single" fact, but 

 that there are many facts, by which the history of South 

 America is connected with that of North America. 



BENJAMIN SMITH BARTON* 

 Philadelphia, 



January the l^thy 1812. 



XI. 



On fJie Production of Electrical Excitement by Frictiofi^ 

 By J. D. Maycock, 31. D, 



Law of elec- 

 trical cxciCe- 

 ment. 



It is general; 



To W. NICHOLSON, Esq, 



SIR, 



JL HE interesting discoveries of Wilcke^ JElpiritis, Volta^ 

 and other exjierimenters on the two electricities, togethef 

 with the result of several experiments by Dr. Davy*, and 

 the facts, which I lately communicated to yout> lead, by a 

 fair induction, to a general law, which may be thus expres* 

 sed : The contact and separation of dissimilar bodies operate 

 as a cause of electrical excitement ; and the chargCi which is 

 assumed., afier separation, by one body, is precisely opposite to 

 that, which is acquired by the other. 



The existence of this law, in relation to a variety of bo* 

 dies,' isfuily demoiistrated; and, asfar as the investigation 

 has proceeded, it nppears to ufTect all in a greater or less de- 

 gree: 1 think, therefore, we are warranted, by every princi- 



* Fhllos. Trans. 1807. 



t Journ. vol. XXIX. 



pie 



