Dr Colquhoun on the Argillaceous Ore of Iron, 73 



themselves, and also in the nature, extent, and relative position 

 of the beds of other minerals which are contiguous to them. 

 Sometimes the several strata of ore have a considerable num- 

 ber of layers of argillaceous schist, as slate-clay, clay-slate, bi- 

 tuminous schale. Sec, or coal, or limestone interposed in every 

 variety of arrangement between them ; and more rarely there 

 are found to be beds of marie, sandstone, indurated clav? &c., 

 which similarly alternate with these strata of ore, and with 

 each other. But it does not always happen that two strata of 

 the ore are separated by any number of interposed minerals, 

 or that they are situated at any distance whatever from each 

 other in the coal formation. They are often found lying the 

 one superimposed immediately upon the other, and yet each 

 completely distinct in its properties and composition. It is 

 indeed impossible to discover any general principle of arrange- 

 ment as prevailing among the various strata which compose 

 the coal basin. 



In so far as we have hitherto examined, the general geolo- 

 gical character of the iron-ore is completely analogous to that 

 of the other minerals composing the coal formation. There is, 

 however, one very decided and anomalous peculiarity of occa- 

 sional occurrence, which distinguishes it from all the others. 

 It is not always met with in the shape of a continuous strati- 

 fied mass, as the schist, the coal, the limestone occur in their 

 Respective beds ; but on the contrary, it is very frequently dis- 

 tributed in distinct, independent nodules which are found im- 

 bedded, in very different degrees of abundance, in some other 

 mineral. It sometimes happens that these nodules lie in a 

 horizontal position, and at regular distances from one another, 

 forming, in fact, a regular stratum, which is excavated as eager- 

 ly by the ironsmelter as the ordinary uninterrupted strata. 

 More frequently, however, they are disseminated in the most 

 promiscuous manner throughout the whole extent of the stra- 

 tum in which they exist imbedded, and are found abundantly 

 in some parts of the stratum, while in others not far distant, 

 they are altogether wanting. A regular stratification of no- 

 dules is termed a line of balls by the miners ; when irregularly 

 diffused, they are called flying balls or lunkers. The former 

 seem to occur exclusively in argillaceous schist, the latter, for 



