£24 Dr Colqulioiin on the Jjs^illaceous- Ore (rf Iron, 



ly the same constitution as the sparry iron ore, and were 

 composed of the protoxide of iron united with carbonic acid. 

 The principal difference between the sparry ore and the others 

 was a mechanical one, deducible probably from some local cir- 

 cumstance incident to their original formation, which may have 

 caused their intermixture with a variable quantity of clay in 

 addition to those ingredients which they possessed in common 

 with the former ore. But as the amount of this clay was often 

 very inconsiderable, Descostils proposed that the ore should no 

 longer be termed an argillaceous ironstone, but simply carbo^ 

 nate of iron, distinguishing it, however, by the less definite 

 epithets of earthy or amorphous. He was induced to suggest 

 this nomenclature, nof merely as being less inaccurate in itself, 

 but also because the term argillaceous might prove injurious to 

 practical men, as he states that he had often known iron smel- 

 ters introduce a large supply of siliceous and calcareous mine- 

 rals into their smelting furnace, in order to flux the imaginary 

 quantity of clay with which they supposed the ore to be con- 

 taminated. The appellation thus suggested, however, has never 

 found its way into general practice. 



Another result of great interest was deduced from these in- 

 quiries of Descostils. Although the specimens of iron ore ex- 

 amined by him had been collected from very different localities 

 in France, and also from England, they all agreed in one re- 

 spect, that they had been found in districts abounding with 

 coal. And the whole of his researches led to the conclusion, 

 that there subsisted a very intimate geological connection be- 

 tween coal and the argillaceous carbonate of iron ; a connection 

 so close that the miner might almost with certainty regard the 

 presence of the one mineral as a proof of the vicinity of the 

 other. But it is difficult to overcome the force of a rooted pre- 

 judice. Although the memoir of Descostils must at once have 

 carried the conviction to the minds of men of science, that the 

 most useful ironstone was co-existent with the beds of coal in 

 the various coal-districts of France, yet the nation at large for 

 a long period refused to believe that they possessed such a 

 treasure within themselves, and obstinately persisted in re- 

 garding the island of Britain as the envied and exclusive de- 

 pository of that ore. Even after many of the cleves of the 



