186 Miscellanies. 



of the moon-culminating stars, which are observed at the same time 

 with the meridian circle. For, latitude, the transit is placed east and 

 west. 



The Altona Observatory may serve as a model of such a small 

 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 

 practiced 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 compound of plati- 

 num, 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 cr^'stals, 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 copi- 

 ously evolved, and the deutochloride of platinum remaining in so- 

 lution. 



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 

 water, just sufficient in quantity to preserve the mass in a serai-fluid 

 condition, and to prevent the precipitation of any deutochloride of 

 platinum. 



