168 



On the Difference in the Appearance of the Teeth and the Shape of the 

 Skull in different Species of Seals. By Sir Everard Home, Bart. 

 V.P.R.S. Read February 28, 1822. [Phil. Trans. 1822, p. 239.] 



In this paper, which is illustrated by three drawings, Sir Everard 

 brings before the Society an account of some peculiarities in the 

 skull and teeth of different species of Seals, in order to prevent mis- 

 takes being made when fossil remains of that animal are met with. 

 The first drawing is of the skull of the large seal, from the South 

 Seas ; the second, from a seal shot near the Orkneys ; and the third, 

 from a seal's skull in the Museum of the College of Surgeons, from 

 New Georgia, near the ice towards the South Pole. In all these the 

 teeth differ in form, which the author suggests may arise from the 

 shell fish on which they live being of different kinds. 



Experiments and Observations on the Development of Magnetical 

 Properties in Steel and Iron by Percussion. By William Scoresby, 

 Jun. Esq. Communicated by Sir Humphry Davy, Bart. P.R.S, 

 -Read March 7, 1822. [Phil. Trans. 1822, p. 241.] 



The result of the experiments detailed in this paper are, that 

 merely hammering a bar of soft steel upon pewter and upon stone, 

 gives it a feeble magnetic power ; but that the same bar hammered 

 vertically upon a poker, became much more powerfully magnetic. 

 On inverting the bar a single blow nearly destroyed its magnetism, 

 while the effect of two blows was to change the poles. Several 

 blows upon the end of the bar when in the plane of the magnetic 

 equator, also destroyed polarity. Increase in the length of the bars 

 augmented the magnetism thus given by percussion. A strong mag- 

 net properly tempered was uniformly injured by hammering, but 

 most rapidly when the north pole was upwards ; after the magnetism, 

 however, had been thus reduced to a certain extent, the power be^ 

 came nearly stationary, so that striking it in any position with the 

 same hammer, occasioned scarcely any change of intensity. 



The strong magnetizing effect of percussion on soft steel, induced 

 Mr. Scoresby to apply the property to the formation of magnets, and 

 he succeeded in giving to them considerable lifting powers, every 

 care being taken to exclude all magnetic substances, and especially 

 to free the bars of magnetism before the experiment. 



The author also examined the effects of percussion upon soft steel 

 magnets, and upon cast iron. 



A soft steel magnet, lifting 1000 grains, when placed vertically 

 upon a poker, with its north pole upwards, had its magnetism de- 

 stroyed by five blows. 



A bar of soft iron hammered vertically upon the poker could not 

 be made to lift more than between 6 and 1 1 grains. A cast iron bar 

 of the same size, and similarly treated, lifted 37 grains, and, having 

 acquired this power, its magnetism was nearly destroyed by five 

 blows with the north pole upwards. 



