244 Professor Gmelin on a New Formation 



syphon, in a direction nearly parallel with the leg, the liquid 

 is raised over the bend, and thus begins to flow without the 

 inconvenient process of filling it as is usual. That the wind 

 does diminish or augment the vertical pressure of the atmo- 

 sphere sufficiently to account for the variations of the barome- 

 ter I will not venture to assert ; but a friend once told me, 

 that he had found his barometer so unsteady whilst in a pas- 

 sage where there was a draught, that he was obliged to 

 move it. 



The learned Professor proposes a new theory of the varia- 

 tions of the barometer, the principle of which is, " That as a 

 horizontal current of air must, from the form of the earth, 

 continually deflect from its rectilineal course, such a deflection 

 being of the same nature as a centrifugal force, must diminish 

 the weight or pressure of the fluid.'" This may be sufficient 

 to account for the fall of the barometer in high winds, but it 

 necessarily ascribes the rise of it to a cause merely negative, 

 viz., the absence of wind, yet the rise of the barometer in a 

 north-east wind is often very considerable. On the other 

 hand, if we consider the north wind as blowing downwards, 

 (which we may perhaps do as coming from a colder region,) 

 the fact accords with Mr Hawksbee's theory. 



E. A.* 



London, January 21th, 1825. 



Art. XII. — On a New Formation of Anhydrous Sulphuric 

 Acid. Observed by C. G. Gmelin, Professor of Chemistry 

 in the University of Tubingen. Communicated by the 

 Author. 



It has been an opinion hitherto received, that anhydrous 

 sulphuric acid can be obtained in no other way, than by de- 

 composing in a distillatory apparatus such sulphates, as, 

 when heated, give off their acid, such as calcined iron-vi- 

 triol. It is generally known, that the fuming oil of vitriol 

 from Nordhausen is procured in this way. 1 have found, 



* We shall be glad to have farther communication with E. A., and 

 learn his address. — Ed. 



