The Burning Cliff's, Lias, Lyme Regis, 561 



bar of steel, of which the magnet is made, need not be more than 

 an inch wide and half an inch thick. As shown in the accompanying 

 figure, two adjustable pole pieces, made of soft iron, fit against 

 the smooth free ends of the limbs, to which they are secured by 

 binding screws. These pole pieces should be about half an inch, 

 wide and rather less than a quarter of an inch thick ; they should 

 be slotted so that the gap between the tips of the poles can be 

 enlarged or diminished according to requirements. The adjacent 

 portions of the pole pieces should be bent downwards, not per- 

 pendicularly, but as shown in the figure, narrowing gradually to 

 a width of about three-eighths of an inch at the tips. The bent down 

 portions of the poles should also thin gradually towards the tips. In 

 this way a fairly strong magnetic field can be obtained between the 

 tips of the adjustable poles. 



Theoretically, a compound magnet should be more efficient than 

 a simple magnet of the same size. In practice, however, one finds 

 that there is no appreciable advantage in using a compound magnet, 

 perhaps owing to the less perfect fitting of the adjustable poles. The 

 use of a simple magnet is therefore recommended, as it is much 

 cheaper and is more readily re-magnetised. 



Using a magnet such as the one here described, a good separation 

 of weakly magnetic minerals can be made. Magnetite, pyrrhotite, 

 and highly magnetic haematite, if present, should first be separated 

 by a small, weak magnet. Ilmenite, garnet, hornblende, augite, 

 hypersthene, etc., can be extracted with the tips of the adjustable 

 poles well apart ; while by bringing the poles nearer together 

 monazite can be extracted quite easily. 



A magnet having approximately the specifications here given was 

 made recently for Mr. A. E. Kitson, F.G.S., by Messrs. Eaird & 

 Tatlock, at the writer's suggestion. It worked quite satisfactorily, 

 although the fittings were in some respects defective. It was found 

 that, using a small trial specimen of ilmenite-monazite-zircon sand, 

 the magnet extracted the ilmenite with the poles well apart ; 

 adjusting the poles with their tips nearer together, the monazite was 

 completely extracted, and an almost perfect separation of the three 

 constituents was thus made. 



This simple permanent magnet is also a useful piece of apparatus 

 for class demonstration. It is comparatively cheap, and a geological 

 laboratory can be equipped with several of them without much 

 expense ; and certainly no course of laboratory work in petrology 

 can be considered complete, that does not equip a student with 

 a practical knowledge of the usefulness of the magnetic method of 

 isolating and separating minerals. 



VII. BUENING ClIPFS. 



TOWARDS the end of January last the inhabitants of Lyme Eegis 

 were somewhat alarmed by the announcement that a portion of 

 the cliffs on the eastern side of the town, towards Black Yen, was 

 "on fire"; a "Full Report of the Volcanic Eruption" was soon 

 afterwards published in the Bridport News for January 24. It was 

 then stated that on Sunday, January 19, " dense vapour appeared at 



DECADE V. — VOL. V. — >fO. XII. 36 



