New Optical Instrument. 155 



the ancient classification adopted for pharmaceutical ex- 

 tracts, divided, according to Rouelle, into gummy, resi- 

 nous, gummo resinous, resino-gummy, and saponaceous 

 extracts ? — Can a more methodical and more exact classifi- 

 cation be established by means of chemical experiments 

 made on the principal substances in pharmacy furnished by 

 extracts ? — Indicate, according to the nature of their dif- 

 ferent constituent principles, the mode of preparation best 

 adapted for each, and the nature of the menstrua which 

 ought to be employed." 



2. " What is the present state of pharmacy in France? 

 what rank does it hold in the healing art ? and what are the 

 ameliorations of which it is susceptible V* 



The prize offered lor the best memoir on the first question 

 is a gold medal of the value of 200 francs. That offered for 

 the best paper on the second question is of the value of 100 

 francs. The memoirs to be transmitted to Paris on or be- 

 fore the 1st of October 1810. 



The following account of a new optical instrument is 

 extracted from a recent French journal: " Jt is well known 

 that the art of perspective consists in representing on a plane 

 surface objects in the position in which the eye perceives 

 them. Descriptive geometry furnishes the means of doina 

 this; but the method which it teaches presupposes science, 

 and demands time. The painter, without having recourse 

 to geometry $ draws on a simple purview from habit and 

 practice in his art. However excellent his eve, and how- 

 ever skilful an artist mav be, he cannot flatter himself 

 with obtaining geometrical preeision. A new instrument 

 has therefore been invented, by means of which every 

 draftsman, without knowing the rides of perspective, may 

 design with ease and correctness all kinds of subjects on 

 every scale not exceeding 5 decimetres square. This inven- 

 tion belongs to M. Roggcro, of the Conservatory of Arts 

 and Manufactures. 



tc Some very ingenious instruments have been already 

 contrived with this view, and amono; others that of Mr. 

 George Adams, who has been peculiarly distinguished. 

 But from the great number of joints of which the me- 

 chanism is composed, all of these instruments were more 

 or less liable to disadvantages, which M. Roggero's instru- 

 ment has overcome, lie has also united solTditv to preci- 

 sion in the transmission of the movements, besides having 

 furnished his instrument with ;n\ achromatic glass, by 

 means of which we may tracp'the perspective of object's 

 placed at a distance." On 



