f 62 ] 
III. Magnetical Experiments and Obfervatlons . 
By Mr . Tiberius Cavallo, F. R. S. 
(The Ledure founded by the late Henry Baker, Efq. F.R.S.) 
Read November 24, 1785. 
^I^HE objed of this ledure is to (hew the properties of 
JL fome metallic fubftances with refped to magnetifm ; and 
the experiments herein related feem to afcertain fome new and 
remarkable fads. 
The magnetic properties have been generally thought to 
belong only to iron, ortothofe fubftances which contained that 
metal ; comprehending under the general name of iron not 
only the metal commonly fo called, but likewife its more per- 
fect and more imperfed ftates, viz . fteel, iron ores, amongft 
which is confidered the magnet, and the calces of iron, except- 
ing only thofe which are very much dephlogifticated, for they 
poffefs no magnetic property whatfoever. Some other metallic 
fubftances, and efpecially platina, brafs, and nickel, on which 
the magnet has fome adion, were thought to be magnetic fo 
far as they contained fome portion of iron, the prefence of 
which may be matiifefted by chemical methods in many cafes, 
but not always ; becaufe the quantity of iron may be fo excef- 
fively fmall in proportion to the weight of the other metal in 
which it is concealed, as not to be difcoverable by chemical 
analyfis, and yet it may be fufficient to affed the magnetic 
needle. 
