TRANSACTIONS OF THE SECTIONS. 
51 
tough in this instance the direction of operation of the adjusting magnets was hut 
incidental, the effect, so far as the authorized reports may guide us, was fatalso 
''it had there been no adjusting magnets the captain would have been guarded 
ininst the delusion that he was making a fair course down the Channel, and would 
Wt been in a very different position as to safety. 
Tn magnetic condition of iron ships and the circumstances under which the cniei 
- mity of their magnetic action was developed, could be well illustrated by a few 
i ninenti with an iron bar—as first, showing the simple effects of the earth s 
■luttion, and secondly, the augmenting or changing influence of mechanical 
irate. Thus, an iron bar, entirely neutral as to its molecular magnetism, as 
>' J*o by its being devoid of influence when placed horizontally, in an east and west 
>. near a compass, became strongly magnetic when placed upright, or proximately 
11 but its polarity was reversed by turning it with the contrary end downwards, 
1>j ‘i again became neutral when laid on the horizontal east and west line. II the 
" ■ l ); ir, however, while held in an upright position, or inclined in the axial 
‘Ui jn ol the earth’s magnetism, were subjected to percussion or other mechanical 
-ccf, not only did its magnetism become much more powerful than that of simple 
•--'ion, but it strongly exhibited its augmented polarity, when placed in the east 
**• equatorial position, and, however it might be moved about and swung 
r jj-MU polarity remained the same. 
proved these two propositions by experiment. Dr, Scoresby went on to 
. r*-y them to the case of iron ships, and to point out that, in consequence of the 
, Action to which the material was exposed while the ships were in course 
■ |On,tnictioD, it became as intensely magnetic as it was possible for malleable iron 
iJ a ' s ““Panted magnetism, however, was not permanent or fixed, but, 
r> I went circumstances, as to the relative directions of the ship’s magnetism 
i*. D ' . ear ^> was easily changeable, and liable necessarily to be changed. 
_ , ‘‘S'letisin developed by mechanical violence conld be readily neutralized, or 
1 to .’tu . a . P ru P er change uf conditions, by other processes of mechanical 
i hU8 > l / bar of iron magnetized by hammering were held in tlic reverse 
I that in which the magnetism had been developed, and again ham- 
--«i,'r,iS* P v 0la l nt 5 r ' would lint only be altered, but reversed. Again, after well 
' rtk „?!„ m a ve| "tical position, let it be quietly reversed, the lower end, 
. „ im-tonf hammered, now being upwards, and let one of its extremities be 
. , » • nted to a delicate compass : the deviating influence in this ease would be 
<t .L|| te(l , t0 a delicate compass ; the deviating influence in this case would be 
mj„ a few degrees only, from the influence of the earth s magne ism 
- ion the Wgmented magnetism of the bar. It. while held in this 
n to flv rnS b,0W were s'tuck on the bar with a hammer, the needle would be 
• tiin-H Unr l as 11 b y mri gic. and settle at a point of deviation perhaps four or 
V* r ln, Kreut “ before. • . , 
1 ' l |tLi 0t a ‘J otlle1, experiment which he was in the habit of showing wit 
' ^ wasSn 0 lron ' t0 elucidate the phttinomcoa of mechanical vtbrahoiis or 
Ui ( l (I.! more rc 'narkaide. Here be should employ ft couple of thin iron 
•' r »l, that7 K 0n !^ h other,—and it would be seen, when their condition was 
a*;™ .“S 11 held close to the compass, horizontally cant afld west, there 
1 aotinn ...i , tu me compass, normoniuiiv 
whatever on thc need | e . But artcr holdimr the plates upright and 
" 1 tiflLrrr sli 8 ht, y« or diking them with the hand, or merely g» v 
‘ V ' J " found 5 » 18 u C ' anfl theu presenting them us before to the c°tnpn*s, 
rn "rd le . 0 have become very strongly magnetic, thc end wbiCh 
north pole of thc needle. Reversing the position of 
* fur, uerlv re!5i- u P ri 8 ht » let the vibratory action be repeated, and 
m ... ?."spMhn* u,;ii u„ e i. .. : .i....i. RroeatiDK 
the 
' ,rT »crlv rPn ,ii- npfght. Jet the vibratory action be repeaieu, 
,rVflr y action '!‘, n f "'I 11 novv he found to attract the north pole. Repeating the 
ZS*** bM l.nri*ontaIly 
, ■'SneUsm *" v F'«wm were uem horizontally *m 
a| l a5J? d «.** founi1 * on bringing tho plates to the test, to have disap- 
having gone. 
■ lce t ohifTti,.., , ™ ,n pMB Having gone. . ... 
Q a J? 08 which might be probably offered against the application of his 
an «‘ “nail bars to the case of iron ships, he had made 
i.. i .."mica i r,... .. . ... ... ... . eli ms were 
r>. , "‘s on rr.ii \ • a, u«m oars iu uie cast- oi *»•«■ r .. 
ihatc-s. of the same kind as those of which ships were 
' ^ coinrji - h a(i ascertained that the magnetism in these also was chat g - 
&ble llk e that in bar iron, under the requisite change of position, by 
4* 
