718 



TEST OF IKON BY MAGNETISM. 



section was seen to have the appearance indi- 

 cated by B. It had a considerable crack, 

 amounting to a cavity, as shown in the cut, and 

 the structure surrounding this crack was partly 

 crystallized and partly fibrous. 



Into a piece of 1 in. gas-pipe had been in- 

 serted, unknown to Mr. Saxby, an iron plug at 

 each end (Fig. 11). The magnet soon detected 



1 in. round. Length 16 ins. 



the central break in the continuity of the iron 

 mass, as shown by the position of Mr. Saxby's 

 mark at A. A somewhat similar case was 

 that of a bar (Fig. 12), 1 in. in diameter and 



FIG. 12. 



j round. Length 16" ius. 



16 in. long, which was drilled from end to end 

 with a in. hole. A short steel bolt was fitted 

 into the middle of the bar, and $ in. iron was 

 welded into both ends. The small cross in the 

 middle of the cut shows the centre of the steel 

 bolt as determined, and the two other crosses 

 indicate small faults of course unknown to 

 the smiths. A bar (Fig. 13), welded together 



FIG. 13. 



BEST HALF OF EAR 



O 



C/ommon irou. 



out of a piece of Bowling and a piece of com- 

 mon iron, had, at about its middle, a drilled 

 hole, into which a magnetized steel pin had 

 been riveted. The compass -magnet soon 

 found out the pin, the difference in quality of 

 tho two ends of the bar, and also an unsus- 

 pected fault at the end, indicated by the zig- 

 zag line. A bar of round iron (Fig. 14) was 

 FIG. 14. 



Common. Galvanized bar. Bowline'. 



brought to him painted over ; it had been 



"jumped together" in three different pieces 



and qualities of iron a bar worked up out of 



scrap of galvanized iron, another of common 



iron, and the third of Bowling, as illustrated 



in the cut. The needle detected very unequal 



qualities, the verdict being that the bar was 



FIG. 15. 



Magnetic iron ore. 



|A|B' I W ROUND j > LENGTH 22." 



1 



the lathe, was put into Mr. Saxby's hands. It 

 was 1 in. in diameter, 22 in. long. He soon 

 pronounced one end to be better than the 

 other, and was accordingly told that the end 

 to the left of the cut was of the best Yorkshire 

 Bowling. The compass-magnet showed the 

 bar to be faulty at A and B, where marked. 

 It was then explained that the best end of the 

 bar had been screwed into the tapped end of 

 the other, a small space at B being filled with 

 magnetic iron ore. The length of the screw, 

 together with the cavity, is about 2 in., and 

 the points A and B indicate the end of the 

 cavity and shoulder of the bar at the base of 

 the screw. Two small unsuspected defects 

 were also found, and their existence proved 

 by cutting the bar at A' and B', the slight de- 

 fects being attempted to be shown in the wood- 

 cuts A' and B'. The following is a very re- 

 markable experiment, and it affords much food 

 for thought. A 4 in. round bar, Fig. 16, 14 in. 

 Fro. 16. 



r.lN ROUND' 



A 03 c| 



long, had a % in. hole drilled 

 into it at one end, into which 

 a bolt of unma<rnetized steel 

 was inserted and welded up 

 with the end of the iron bar. 

 The magnet detected a spot as 

 marked by a scroll in the up- 

 per figure, but its other end could not be found. 

 The needle only testified to a weakening of the 

 magnetism as if toward the right hand of the 

 FIG. 17. 



unfit for being manufactured into any article, mark. From this it was inferred that this 

 The bar, Fig. 15, bright as if just turned up in mark showed an unwelded portion of the bolt, 



