found hi the Marble of Carrara. 27 



Such was the state of the question when M. Repetti pub- 

 lished his work in 1820. Since that time he has inserted in 

 the Anthologia an observation which he made along with M. 

 Pompeo Pironi, a naturalist of Milan, and which appeared to 

 him to remove every doubt. 



" In passing," says he, " to the vvest of the Foce della Bru- 

 ciana, I observed accidentally a micaceous marly rock of a 

 chestnut colour, and of the kind which the French call molasses 

 where, if I may use the expression, nature was caught in the 

 fact. 



" In a vertical section of the ground contiguous to the new 

 road, I observed some veins or contorted fissures which tra- 

 versed the mass of marl, and were covered with quartz and 

 calcareous spar, and from which there issued, as if the water 

 of infiltration pushed it from within outwards, a substance 

 transparent and viscid between the fingers., like the gum 

 which eocudes from trees. 



" I immediately recollected the fine experiments of Berze- 

 lius, by which he showed that one of the characteristic pro- 

 perties of .9z/e<2? was, that it precipitated itself from solution in a 

 gelatinous form, and the phenomenon quoted in my work on 

 a pasty mass found in 1819, in an anhydrous geode of Carrara 

 marble. I was instantly satisfied that the fact which I had 

 discovered afforded an irrefragable proof of the recent forma- 

 tion of quartz crystals in the cavities and fissures of calcareous 

 rocks. 



" My first care was to extract from the fissure a portion of 

 the semifluid substance, and to wrap it up in a sheet of paper, 

 with the view of submitting it to chemical analysis. I also 

 thought of impressing upon it some figure which might prove, 

 in the event of its becoming solid, that it had been originally 

 fluid, but its extreme liquidity prevented me from doing 

 this. 



" In the evening of the very day on which I discovered it, 

 I found that the paste contained in my sheet of paper had be- 

 come solid, opaque, friable, rough to the touch, and of a zMte 

 tint:' 



In the remainder of his paper, M. Repetti relates a series 



