94 



Observatory, and the yearly journeys of the Russian Astronomers 

 from Dorpat, as models for the use of the instruments in determining 

 geographical positions. The observations of Professor Schwerdt, of 

 Spire, will be found useful in the application of the meridian circle. 



Such a small Observatory will be well adapted to form observers ; 

 as the art of handling instruments so as to obtain accurate results is 

 only to be acquired by practice. 



Dr. Patterson made the following verbal communication: — 



That the use of the wax tablet written on with an iron stylus, as 

 practised by the ancient Romans, had been tried, for the first time, 

 this day, at the Pennsylvania Institution for the Instruction of the 

 Blind, and that the success had been perfectly satisfactory. The 

 blind read, with ease, the words written, traced geometrical figures, 

 &c. It is confidently believed that the Roman tablet will prove of 

 great importance in the instruction of the blind. 



Professor H. D. Rogers made a verbal communication, in 

 which he called the attention of the Society to a new com- 

 pound of platinum, discovered by himself and his friend, 

 Martin H. Boye; upon the further investigation of which they 

 are at present occupied. 



It is a well characterized salt, composed of the deutochloride of 

 platinum, and the binoxide of nitrogen, in which the former may be 

 conceived, in accordance with the views of Professor Hare, to act the 

 part of an acid, while the binoxide of nitrogen is in the relation of a 

 base. It is of a bright gamboge yellow, is distinctly crystalline, 

 though, in consequence of the minuteness of the crystals, their form 

 has not been determined. It is highly deliquescent, absorbing water 

 at ordinary temperatures, with great avidity, from the atmosphere. 



It is rapidly decomposed by the mere addition of water, which 

 causes an active effervescence; the binoxide of nitrogen being 

 copiously evolved, and the deutochloride of platinum remaining in 

 solution. 



This interesting compound is best procured by evaporating a solu- 

 tion of platinum in aqua regia nearly to dryness, and then adding a 

 large excess of fresh nitro-muriatic acid by small quantities at a time. 

 The compound may thus be readily procured by filtering and press- 

 ing the powder between folds of bibulous paper. Should the con- 

 centration of the liquid be carried too far, it is requisite to add a little 



