n8 Mr . Barlow on the anomalous magnetic action 
magnetic action, when rendered perfectly soft by being heated 
in a furnace. With this view, bars of equal size of cast iron, 
malleable iron, shear steel, &c. were rendered white hot, and 
being placed in the direction of the dip, as before, their pow- 
ers, as was anticipated, agreed nearly with each other ; but 
still the cast iron, which was weakest while the metal was 
cold, exceeded a little in power all the others when hot, and 
the malleable iron which had the greatest power cold, had 
the least when hot ; but the difference was not very great, 
and might probably arise from some accidental circumstance. 
While carrying on these experiments, it had been observed, 
both by Mr. Bonnycastle and myself, that between the 
white heat of the metal, when all magnetic action was lost, 
and the blood-red heat, at which it was the strongest, there 
was an intermediate state in which the iron attracted the 
needle the contrary way to what it did when it was cold, viz. 
if the bar and compass were so situated that the north end of 
the needle was drawn towards it when cold, the south end 
was attracted during the interval above alluded to, or while 
the iron was passing through the shades of colour denoted 
by the workman the bright red and red heat. 
As this anomalous action had never before been noticed, I 
was desirous of examining it a little more particularly, and 
with the assistance of Mr. Bonnycastle, the following series 
of experiments were performed, wholly directed to this in- 
quiry. Before entering upon the detail, however, it may not 
be amiss to notice those results which have hitherto been ob- 
tained relative to the magnetic action of heated iron ; and to 
show how the contradictory statements, that we find on the 
subject, may be reconciled with each other. For example : we 
