FACTITIOUS PUZZOLANA. S31 



Mr. Hatchett put his difcovery to the teft of real prance, Leather made 

 having actually convert*! /kins into leather by the artificial tan J n * he artlfiaaI 

 procured as delcribed, but obferves, that the production of 

 this fubftance, for the prefent, muft be confidered only a 

 curious chemical facl, not altogether unimportant, and not 

 capable of economical application, though he hopes, that Hope of Its 

 hereafter a procefs may be difcovered for preparing this ^? o ^ cal pro " 

 fpecies of tan fufficiently cheap to enable tanners to ufe it 

 in their bufinefs. 



There is reafon to fuppofe, that it would be fuperior to Reafon for 

 common tan for this purpcfe, as it appears from experiments thinking it 

 mentioned in Mr. Hatchett's fecond paper on the fame fubjecl mon tan# 

 (which will be given in the next number) that ft folutions of 

 the artificial tanning fubltance feem to be completely im^u- 

 trefcible, neither do they ever become mouldy like the infu- 

 fions of galls, fumacb, catechu, &c/'* 



VII. 



Memoir on the Difcovery of a Factitious Puzzolana, prefaited 

 to the French National Injiitute, by M. Dodun, Engineer in 

 Chief of Bridges and Highways in France f. 



A HE depofited dud of ancient volcanic fubftances, has been Factious puz. 

 long u fed in Flanders, and the adjacent countries, as a fub- zolanaof 

 flitute for the Italian puzzolana, under the name of trafs, or * 



ajlies of Tournai. 



M. Faujas has proved by decifive experiments, made by that of Faujas. 

 order of government, that certain lutulent eruptions of 

 ancient volcanoes at Vivarais, had the fame qualities as the 



* The peculiar tanning property of the water of certain peat 

 bogs and moraifes, may be otherwife accounted for, than by Mr. 

 HatcWett's fuppoiition, by the fact, that peat is not uniformly the 

 production of the fame vegetable fubftances : wherever heath, 

 tormentil, and perhaps fome other plants, are found in abundance, 

 the peat water will have this quality ; in the cafe of heath, at leafr, 

 it cannot be doubted; 3nd perhaps the peat which does not yield 

 tan may owe this deficiency to the total abfentfe of vegetables of 

 this fpecies.' — B. 



f Journal Ue Phyjiaue, Tom, 6!. 



puzzolana 



