250 
SECTION III. 
(Read February 2Ist, 1843.) 
90. The results which I have arrived at, whilst 
repeating the interesting experiments on highly 
heated iron, first instituted by Mr. Barlow, and 
others already detailed in a former section of this 
memoir, have shown in the most satisfactory 
manner, that the magnetic forces of the earth, 
in this latitude at least, have no power what” 
ever in rendering highly heated iron magnetic? 
whether that iron be in solid masses, or in the 
shape of hollow tubes. 
91. I have already taken advantage of this 
important fact, as being favourable to my views, 
respecting the entire expulsion of the magnetic 
matter naturally belonging to the iron, by the 
intreduction of so great a quantity of calorific 
matter as was forced into the metal by the pro- 
cess of heating. But as the polarizing powers 
of terrestrial magnetism are exceedingly feeble 
