Dialysis. 381 



by the French, astronomers of the unfavourable atmosphere of 

 Paris, the new telescope will be placed in an observatory to be 

 erected in the south, and specially devoted to original investi- 

 gations. 



On the 28th ult., M. Le Verrier exhibited to the Academy a 

 drawing representing the double nebula in Canes Yenatici — the 

 wonderful spiral formation of which was made known through 

 the magnificent instrument at Parsonstown — as seen by the 

 Foitcault mirror. The Abbe Moigno tells us that the drawing 

 exhibits " incomparably more details than those given by Her- 

 schel and Lord Posse." If this be correct, the Foucault tele- 

 scope must possess an enormous advantage over the old form 

 of reflectors, as the diameter of the new instrument is less than 

 half that at Parsonstown. 



We understand that four-inch instruments of this descrip- 

 tion, in a square mahogany frame, elevated or depressed by a 

 rack movement like that of a reading-desk, may be had in Paris 

 for ten pounds. They are, however, liable to become tarnished, 

 when they need an inexpensive process of repair. 



DIALYSIS. 



'BY W. B. TEGETMEIER. 



The application of the researches of Mr. Graham respecting 

 the diffusion of liquids to the purposes of practical chemistry 

 and the arts of civilization, offers one of the most interesting- 

 examples of the eventual tendency of even the most abstract 

 scientific investigations to become practical, and so to aid in pro- 

 moting the comfort and welfare of mankiud. It is almost impos- 

 sible to imagine a subject offering apparently less practical ad- 

 vantages than does the admixture of two liquids with each other, 

 and yet from the rigorous and scientific investigation of the phe- 

 nomena of their mutual diffusion, and the laws which regulate 

 its operation, has sprung the new method of dialysis, which pro- 

 mises to revolutionize a very large number of chemical opera- 

 tions, and to introduce new methods of maunfacture into the 

 arts that will entirely subvert many existing processes. 



The subject is so interesting and so novel in its practical 

 bearings, that it will be desirable to trace its gradual develop- 

 ment from an abstract scientific truth to its present useful appli- 

 cations. Mr. T. Graham, the Master of the Mint, has long held 

 a very high position among the most eminent scientific chemists 

 that this country has produced; among other subjects that 

 were diligently investigated by him some years since were the 

 laws which regulate the mutual diffusion of gases. The in- 



