Sir E. I. Murchison tf« /^<? Vents of Hot Vapour in Tuscany. 51 



But I fear I should tire you were I to apply the views I have 

 brought forward to the different phcenomena that followed your 

 discovery of diamagnetism. The pha^nomena of mingled magnetic 

 and diamagnetic substances ; the predominating attraction or 

 repulsion of the axis of crystals ; the phenomena of the magne- 

 crystallic axis ; the currents of induction that a bar of bismuth 

 gives, as shown by M. Weber; — all these consequences follow of 

 themselves in a very simple manner. 



I have the honour to be, Sir, 



Your most humble Servant, 



Dr. VON Feilitzsch, 

 Professor in the Universit// of Greifswald. 



IX. On the Vents of Hot Vapour in Tuscanij,and their Relations 

 to Ancient Lines of Fracture and Eruption. By Sir Roderick 

 Impey Murchison, G.C.St.S., F.R.S., G^S., L.S., Hon. 

 Mem. R.S. Ed., R.I. Ac, Mem. Imp. Ac. Sc. St. Pet., Corr. 

 Mem. Ac. France, Berlin, Turin, i^j-c* 



Introduction. — In surveying the principal localities of those re- 

 markable vents of hot vapour in the Tuscan Maremma, called " La- 

 goni," "Fumacchi," " Funiarole," " Soffioni," "Mofetti," and even 

 " Volcani t," I perceived that their issue took place upon ancient 

 parallel lines of fracture, along which serpentinous and other eruptive 

 rocks had been emitted. As I am not aware that this coincidence in 

 Imes of eruption, acted upon at epochs so remote from each other, has 

 been previously adverted to in any geological account of Tuscan}', I 

 will first call attention to the jjhsenomenon. I shall next take this 

 ojiportunity of expressing my opinion respecting the origin of the 

 " gabbro rosso " of the Tuscans, a rock intimately associated \ritli 

 serpentine ; and, after a brief allusion to recent earthquake shocks 

 along the same lines, the memoir will be terminated by glancing at 

 the simultaneous production of great divergent elevations in Italy and 

 in the Alps, after the deposit of the nummulitic eocene formation. 



Hot vapour vents. — If the intensely hot vapour gusts which have 

 issued for centuries from cavities in the rocks of the Tuscan Maremma 

 had been as well known to Dante, as they were to Targioni Tozzetti 

 their graphic describcr in the last century, the great poet would 



* We are indebted to the Author and to the Geological Society for permission 

 to reprint this highly interesting article from tlie Society's Journal for November, 

 1800.— Ed. 



t For Italian descriptions of the Lagoni, see Gio. Targioni Tozzetti, Viaggi ; 

 Rejietti, Dizionario fisico, &o. dclla Toscaiia, torn. iii. p. 309 ; Bartolini, Atli dei 

 Fisico-critici, toin. vi. p. 335 ; hlascar/ni, Coinnicntario (Siena), 177'J ; Guerrazzi, 

 Contin. dei Georgofili, torn. ii. p. 43.j ; and liepetti, Di/.ion. lisic. stor. ec. della 

 Toscaua, torn. ii. [i. 024, torn. iii. )). 37-1, and Continov. dcgli Atti dei Oeorgolili, 

 toin. \i. p. I'J. 



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