64 Mr William Petrie on the 



A short experience will satisfy an unprejudiced observer that the 

 emancipation of the slaves without previous training in self-control, 

 and in the arts and duties of civilized life, is rather inflicting mis- 

 chief by setting at large a savage who will return to barbarism, than 

 conferring a benefit or raising a fellow creature in the scale of 

 humanity. The author, soon after his arrival, established a place 

 of secure deposit for those blacks who wished to economize their 

 earnings ; founded a system of rewards amongst them for the finest 

 poultry and pigs ; — for the most neatly kept gardens ; — the cleanest 

 houses, and for the best general conduct ; — opened a school for the 

 negro children, and added to the number he found already learning 

 handicrafts. — A strong spirit of emulation was soon excited amongst 

 them ; and subsequent observation shewed that many of the slaves 

 might with equal safety and advantage be entrusted with absolute 

 freedom. Several adults were therefore emancipated ; and the 

 excellence of their subsequent conduct gave gratifying proof that the 

 care and culture bestowed on them had not been in vain. A similar 

 boon was also conferred on many children of parents who, though 

 themselves still slaves, — gave evidence that their offspring would be 

 brought up in habits of order, sobriety, and industry. — Where the 

 dominant race counts less than one-fourth of the number of its cap- 

 tives, a social revolution cannot be far distant ; and we hope the 

 free population of so vast an empire will see and profit by an example, 

 which, if regarded in time, may at the eventful period p'eaceably 

 effect that change, which must be otherwise brought about by a 

 catastrophe too horrible to contemplate. — It is a fact well known in 

 the interior of Brazil that the greater scarcity and higher price of 

 slaves now than formerly, ensures that unfortunate race much better 

 treatment at present than they received when their loss could be 

 supplied from the market, at the low rate which anciently prevailed ; 

 a fact acknowledged by every native slave-owner. This scarcity, 

 greater value and increased comfort, are all the results of our 

 blockade ; and thus the blessing of British humanity is daily felt by 

 the captive in the remotest corner of Brazil. 



This paper was of very great length, and contained numerous 

 descriptions of mines and scenery ; it was illustrated by an extensive 

 and beautiful suite of gold specimens on the table. 



On the Dynamic Equivalent of Current Electricity, and on a 

 fixed Scale for Electromotive Force in Galvanometry . By 

 Mr William Petkie. Communicated by the Author. 



The dynamic value of a current of voltaic electricity is 

 represented by the product of the rate at which electro-che- 



