Astronomical and Nautical Collections. 125 



observation. At the moment when the magnetic pole passes 

 through this point, the declination or variation will ob- 

 viously be a maximum, while the change of inclination will 

 as obviously be greater than in any other part of the orbit, 

 other things being supposed equal : since the pole will be 

 moving directly to or from the place of observation. On 

 the other hand, the change of declination will probably be 

 the most rapid when the dip is the greatest, as it probably 

 was in London and Paris, towards the middle of the 17th cen- 

 tury, or a little later, the declination itself being inconsider- 

 able, or somewhat westerly, because the nearest point of the 

 orbit seems to be on that side of the true meridian of London. 

 It is singular that this useful little almanac should an- 

 nually present to the public, among the ** Epochs of the 

 principal discoveries in Geography," that of the Canary- 

 Islands, by the Genoese and Catalonian navigators in 1345; 

 while there seems to be no reason for doubting that these 

 islands were well known to the ancients, one of them being 

 described by Pliny under the name of Canaria. (vi. 32.)] 



iii. Experiments on the effect of the direct white Light of 

 the Sun in making Steel Magnetic. By Mr. A. Baum- 

 GARTNER, of Vienna. Ann. Chim. Nov. 1826. 



When I was repeating, in the course of last summer, the 

 experiments of Mrs. Somerville, on the effect of the sun's 

 coloured light in making steel magnetic, I discovered a 

 process wliich appeared to succeed more rapidl}^ and more 

 certainly than that which Mr. Morichiniand Mrs. Somerville 

 employed. It led me to this conclusion, that a piece of 

 steel, of the size of a common knitting needle, of which one 

 or several parts are polished, and the remainder unpolished, 

 when exposed to the direct white light of the sun, acquires 

 the properties of a north pole at each polished part, and a 

 south pole at each unpolished part. The process that I have 

 employed is the following : 



I took a piece of English steel, of the size of a common 

 knitting needle, and heated it till it became covered with 

 black oxyd ; I then removed the oxyd at one or more parts, 

 by rubbing it on a hone with oil, and finished the polishing 



