33t FACTITIOUS PUZZOLANA. 



port was coloured green, and fmall grains of iron were feen 

 to pafs firft of a dark-green colour, then of a bright green, and 

 afterwards to difappear in evaporating. There remained on 

 the globule only a flight tinge of blackifli-green. 

 General refult. The refult of all thefe fads teems tc be, that this oxide is 

 entirely deprived of its metallic principle, and that its fuper- 

 oxigenation renders it reducible and refractory. 

 The oxide may The ar i s ma y draw fome advantage from thefe oxides, by 

 mentt ufing them in pigments for buildings. I fucceeded after many 



warnings, in extracting from them a beautiful brown-red 

 colour equal to that of commerce, and applied it to ufe fuc- 

 cefsfully.* 



* This paper has been abridged in its introduction, in the details 

 relative to negociations with the Conftituent Affembly, and in fome 

 other points a little irrelevant to the puzzolana ; but all matters 

 directly tending to illuftrate its nature and properties have been 

 carefully copied. 



M. Dodun's difcovery may be of fome ufe to this country, as 

 there are in many parts of it large mafles of iron-ftone, and fome 

 is found in the vicinity of moft coal-mines. 



It has been long known that iron ochres have the fame property 

 of forming puzzolana with lime, when properly roafted, and this 

 circumftance is mentioned at large in Chaptal's Chemiftry. A pa- 

 tent has alfo been obtained in this country for the application of 

 iron pyrites to the fame purpofe, the right to which was purchafed 

 l»ng ago by Mr. Samuel Wyat. But the novelty of M. Dodun's 

 difcovery is, that poor iron-ftone is equally fit for this ufe, as the 

 other fubftances mentioned, which is of the more importance as 

 it is very plentiful, and may often be procured in fituations where 

 the others cannot. 



It may not be amifs to mention here, that bafalt treated in the 

 feme manner, has the fame property as the puzzolana : the whin- 

 ftone, of which the ovoidal paving-ftones confift moftly, is of this 

 kind ; and it is found in great abundance in thefe countries, in 

 different forms. — B. 



Experiments 



