210 Proceedings of the 



inserted between the poles of the same magnet. The experiments 

 by Messrs. Babbage, Hersehel, Nobili, Christie, and others, were 

 referred to, and M. Arago's objections to the theory which has been 

 advanced stated and illustrated. The opinion entertained has been, 

 that the magnet produces poles of an opposite nature to its own at 

 the parts where they approach nearest to the copper, and that these 

 poles are not assumed and destroyed instantaneously, but require 

 a certain portion of time for their formation and destruction, in 

 consequence of which they exert an attractive force on the poles 

 which are passing over and from them, and drag, as it were, after 

 them. M. Arago, however, shows, by the use of the dipping 

 needle, and by long magnetic needles suspended to balances, that 

 the force brought into action is not an attractive, but a repulsive, 

 one ; and states his original objection to the same theory, when 

 it first suggested itself to him, by inquiring how it is that a metal, 

 which, like copper, cannot, when in a state of rest relative to the 

 needle, deflect the latter a single second, can, when in a state of 

 motion, carry it 90° or more. 



An Ornamental Lamp, recently constructed by Mr. Bartholomew, 

 was placed upon the library table at this meeting. Some very 

 elegant transparent paintings and spiral devices were kept in 

 rotary motion, by the action of the current of heated air issuing 

 from the chimney of the lamp. The contrivance appears well 

 adapted to a number of purposes of ornamental illumination. A 

 Night Lamp was also shown, invented by Mr. Blackadder. The 

 flame is supplied with oil by capillary attraction, independent of the 

 use of a wick. 



Numerous Books, presented to the Institution by the Duke of 

 Buckingham, Mr. Smith, and others, were also upon the table. 



Some specimens of Dried Plants, from Massachusetts, were pre- 

 sented by Mr. Sharpe, of Boston. They were in the form of lon- 

 gitudinal cakes, about eight inches long, four wide, and two in 

 thickness : each cake consisted of the leaves or flowers of a par- 

 ticular herb, which, after being dried and prepared in a peculiar 

 manner, had been then accumulated and pressed together in these 

 forms. The colours were not much injured, and the odours were 

 strong and pure : prepared in this way, it is said that the 

 herbs can be preserved unchanged for a great length of time, 

 whilst they are rendered very portable. The specimens consisted of 

 Thorough- wort leaves, Eupatorium perfoliatum ; Spear-mint, Men- 

 tha viridisi and Elder flowers, Sambucus nigrus. 



