190 BULLETIN OF THE 



feet, its greatest width about 500. The precise position of its flanks 

 is more or less hidden by deposits of drift, but a careful survey with the 

 dipping needle indicates that the deposit has a rudely elliptical form of 

 the above named dimensions, and with the major axis in an approxi- 

 mately north and south position. The rocks which border this deposit 

 are not disclosed at the contact. There are no outcrops within some 

 hundreds of feet of its base. Where found this " country rock " con- 

 sists of syenitic and granitic gneiss and mica schist. These are, indeed, 

 the only materials which have been observed in the immediate neighbor- 

 hood of the hill. 



All the evidence which has been obtained tends to show that this 

 mass of ilmenite is in its nature a dike. The considerations which 

 lead to this conclusion cannot well be discussed in this memoir. They 

 are in general as follows. The rocks of this section of country are 

 evidently steeply tilted. All the exposures which have been observed 

 show dips exceeding thirty degrees of declivity. Therefore, if this iron 

 ore were a bedded deposit, it would probably appear along a much 

 longer line than that on which it occurs. We should expect, even 

 allowing for possible faulting, to find the bed repeated at other points in 

 the field. It is true that bedded iron ores sometimes occur in thick 

 pockets, but in no case known to me do these accumulations have the 

 solitary character or the proportions indicated in this deposit. The 

 studies made by M. E. Wads worth appear to afford good petrographic 

 arguments in favor of the hypothesis that this ore has been injected 

 into its present position.* 



A very careful search with the dipping needle, over the fields for a 

 distance of some miles from Iron Hill has failed to show anything which 

 could excite suspicion that similar deposits exist beneath the thick 

 mantle of drift which covers the greater part of this country. A yet 

 more careful exploration for boulders has shown that only a very few 

 small pebbles of this ilmenite exist in the district north, east, or west of 

 the hill, and these are all of a size and shape which make it eminently 

 probable that they have been conveyed to their present site by the 

 aborigines or by the white occupants of the country. 



Pebbles of the Iron Hill peridotite have been more or less employed for 

 various useful purposes, and so have secured a certain measure of arti- 

 ficial distribution. They serve remarkably well for weights, especially 

 those used for fastening horses. They make excellent ballast for boats. 

 They are adapted for heating water, where the heat is communicated to 



* This Bulletin, Vol. VIL (Geol. Series, Vol. I.), p. 183 et seq. 



