MAGNETITE. 297 



hence I thought it would not be altogether a waste of time 

 to put the matter to the test of experiment. Accordingly 

 I had some of the more common ferruginous and magnetic 

 minerals crushed to a fine ])owder, sifted through a INo. 60 

 sieve, and then acted upon by an electro-magnet under 

 water. An electro-magnet was used because it is very 

 difficult to brush off all the magnetic particles from an 

 ordinary permanent bar or hoi'se-shoe magnet, even when 

 the armature is on. The magnet used lifited a weight of 

 18 ounces. A comparatively feeble one was purposely used, 

 so as to attract and remove only those particles which would 

 be attracted by a good ordinary permanent magnet ; a 

 powerful electro-magnet w^ould not have been so suitable for 

 the object in view. 



The crushing was efiected in a porcelain mortar, and 

 finished in an agate one, to prevent access of particles of iron, 

 which of course are always abraded from iron pestles and 

 mortars. The non-magnetic matter can only be separated 

 from the magnetic portions by repeated applications of the 

 magnet and regrinding, because a certain amount of the 

 non-magnetic powder is apt to be entangled with the 

 magnetic. 



Inasmuch as Haematite, Fe203, is often somewhat 

 magnetic, this was chosen as one of the first minerals to be 

 tested for maunetite. 



Hcematite. — A dark comjiact red HcBmatite ; locality 

 unknown, but probably from Elba. Acted on 

 magnetic needle. The powder yielded — 



Grammes. 



Magnetic particles 10-15 



Non-magnetic 56-80 



66-95 

 Or J 5 per cent, of Magnetite. 



2. Hcematite. — Dark red botryoidal massive Haematite, 



mixed with a little quartz. Frizenton, Cumberland, 

 England. Yielded no magnetic particles. 



3. Hcematite. — The same as the last, but a softer variety. 



This also did not yield any magnetic particles. 



4. Micaceous Hcematite. — From the Island of Tanna, 



where it is used by the natives for dusting over the 

 body, for ornamental purposes, on account of its 



