28 Formation of Quartz Crijstals.^cfrom Siliceous Solutions. 



of experiments made at Florence in concert with Professor 

 Taddei, and from which it follows that the pasty substance 

 was composed of 



Silex, - - 5 parts. 



Lime, - - 1 



for the author supposes from the details of his analysis that 

 it was not a simple mixture. 



The reader has, however, before him the elements of the 

 question, and may judge for himself whether or not the obser- 

 vation of M. Repetti is sufficiently precise to obtain sl place in 

 science. Some may perhaps regret that this naturalist did 

 not insist more on the circumstances relating to the transpa- 

 rency of the substance which he analyzed, and that of the large 

 pasty mass extracted from the marble by M. Nero. With re- 

 gard to the objection of Spallanzani it can have no weight, 

 since the phenomena of polarisation have proved that the jellies 

 of oranges and gooseberries are really crystallized, and that 

 they even possess double refraction. 



Art. V. — Facts and Observations relative to the recent Jbr~ 

 motion of Qioartz Crystals^ Sfc. and of indurated Calcedony 

 from Siliceous Solutions and Pastes. 



As we have not been able to procure the original work of M. 

 Repetti, we are glad to have it in our power to lay before our 

 readers the copious extracts from it given in the preceding 

 article, although we had six years ago published in the Ed. 

 Phil. Jcmrnal the simple facts which he had observed. 



The English scientific reader will doubtless partake in the 

 surprise with which we have read the observations of the learn- 

 ed French editor on the paper of M. Repetti. The facts are 

 brought forward as something quite new and unique, as some- 

 thing which geologists have overlooked, and as bordering on 

 the marvellous ; and the reader is told that he must judge for 

 himself whether or not the observation of M. Repetti is suffi- 

 ciently precise to receive a place in science. 

 In England we have been long familiar with analogous and with 



