418 On Metallic Minerals. 



secondary or overlying their supposed igneous origin, 

 appears to receive additional support from the fact, that 

 magnetic iron, a mineral so rare among the secondary class 

 in general should even be characteristic of the trap 

 species, and which the purifying nature of the heat these 

 rocks are supposed to have been subjected to, may 

 account for. 



The neighbourhood of Kingston is remarkable for local 

 attraction, but I believe it is principally confined to the 

 Point Henry side of the river, where the occurrence of 

 amphibolic rocks may occasion it. Mr. M'Donald, in 

 running the boundary line of the military reserve exper- 

 ienced it frequently. Lieutenant Wulf, R. E. noticed a 

 variation of 10° in a distance of about six hundred feet ; 

 and Mr. Markland, in a general report on Kingston, 

 writes — " No mines have as yet been discovered but from 

 the difficulties which surveyors have met with, in running 

 parallel lines, owing to the variations of the needle, there 

 can be no doubt of the existence of iron mines." 



An opinion is too generally entertained that in places 

 where the compass is locally effected, mines of iron may 

 be expected to occur, and that where no such phenomenon 

 exhibits itself, it is useless to seek iron ore. In by far the 

 generality of instances, in which the needle indicates the 

 vicinity of some magnetic body, that body will be found to 

 be a barren rock, containing iron it is true, but in an 

 unavailing quantity, disseminated through the rock in 

 small particles ; to obtain which, in a state of pure iron, 

 the rock itself must be smelted. In the generality of 

 instances also, in which mines occur, they exercise no 

 influence upon the conipass whatever. 



Among the many species of iron ore, there are only two, 



