1888.] 



Magnetic Properties of an Impure Nickel. 



317 



A series of revised rules for handling ships in hurricanes in any 

 part of the world is given. Comparing these rules with the older ones 

 it will be remarked — 



1. That the rule for finding approximately the bearing of the vortex 

 is slightly modified. 



2. That the great rules of the " laying to " tacks remain unaltered. 



3. That the greatest improvement is the recognition of the position 

 and nature of the belt of intensified trade wind on the dangerous 

 side of a hurricane, where a ship experiences increasing wind, without 

 change of direction, and a falling barometer. The old idea that such 

 conditions show that a vessel is then necessarily exactly od the line 

 of advance of a hurricane is erroneous. She may, but she need not 

 be ; and under no circumstances should she run till the barometer has 

 fallen at least 6-10ths of an inch. 



4. There are certain rules which hold for all hurricanes ; but every 

 district has a special series, due to its own local peculiarities. Those 

 for the Southern Indian Ocean are given in this paper. 



YIL -Magnetic Properties of an Impure NickeL" By J. 

 Hopkixsox, F.R.S. Received June 9, 1888. 



[Plates 2—13.] 



The sample of nickel on which these experiments were made was 

 supposed to be fairly pure when the experiments began. A sub- 

 sequent analysis, however, showed its composition to be as follows : — - 



Nickel 95-15 



Cobalt 0-90 



Copper 1*52 



Iron 105 



Carbon 1*17 



Sulphur 0'08 



Phosphorus .... minute trace 



Loss 013 



100-00 



The experiments comprise determinations of the curve of magneti- 

 sation at various temperatures, the magnetising force beiDg increased, 

 that is to say, they are confined to a determination of the ascending 

 curve of magnetisation. The temperature was always produced by 

 enclosing the object to be tested in a double copper casing with an 

 air space between the two shells of the casing, and by heating the 

 casing from without by a bunsen burner. The temperature was 

 measured by determining the electrical resistance of a coil of copper 

 wire. The copper was first roughly tested to ascertain that its 



2 b 2 



