M. f'auquelin on Titanium in Mica. 231 



" M. Vauquelin, at the request of Mr. Peschier of Geneva 

 (who conceived that he had found titanium in several micas in 

 such quantity as to be an essential constituent of the mineral), 

 repeated his experiments, first on two varieties of mica, and 

 afterwards on many others, in all of which he detected the pre- 

 sence of titanium, but in very minute quantity, and in different 

 proportions ; the richest in titanium did not give more than one 

 per cent, of that metal. 



" His mode of analysis was as follows: — He ignited the mica 

 (divided into thin laminae, and cut very small with a pair of 

 scissars), with two parts of caustic potash, for half an hour, and 

 digested the mass in 100 parts of water. Mui'iatic acid was 

 gradually added to the mixture till it was slightly in excess ; 

 the solution evaporated slowly to dryness ; the residuum 

 washed with cold water, and the silica separated by the filter. 



"If the silica was coloured, which often happened, he di- 

 gested it in cold muriatic acid diluted with 10 parts of water, 

 till it became white ; it was then washed, and while still moist 

 boiled in strong muriatic acid. The liquid was then evapo- 

 rated to expel the greater part of the acid, diluted and filtered ; 

 and the solution, containing only a slight excess of acid, treated 

 with an infusion of galls. If titanium was present the solution 

 first assumed a yellowish-red colour, and soon afterwards tan-r 

 nate of titanium separated in flakes of the same colour. ,, 



" The niui'iate of titanium is so easily decomposed by heat, 

 that in general the greater part of the metal is found with the 

 silica, which should always be carefully examined in all ana- 

 lyses in which titanium may be expected to be discovered. If, 

 on the other hand, the evaporation have not been carried far 

 enough, a portion may remain in solution in the washings of 

 the silica. To be certain, j)recipitate the solution by ammo- 

 nia, wash the precipitate, and digest it in caustic potash, which 

 will dissolve tlie alumina and the oxide of titanium, and the 

 latter may then be separated by saturating the alkali with mu- 

 riatic acid, and })recipitation by infusion of galls. 



" Nearly two years since, 1 examined a dark brown mica, 

 from Siberia, for titanium, without finding the least trace of 

 that metal." 



PNEUMATIC MIXHANISM ENABLING THE WALRUS TO CARRY ON' 

 PROGRESSIVE MOTION AGAINST GRAVITY. 



Sir Everard Home's papers containing his discoveries of 

 the pneumatic mechanism enabling the fly and the gecko to 

 caiiv on progressive motion against gravity are already well 

 known to our readers. The following is his account of an 



analofjous 



