OF THE EARTH’S MAGNETISM. 517 
times of minimum force) are near the epochs of mean temperature; and one 
maximum was before the time of maximum, the other before that of minimum 
temperature. It was very improbable, however, if the process employed for the 
determination of the temperature coefficient had in this case given such a result 
by chance, that it could happen in any other instance. The Toronto observa- 
tions for 1842 were, however, discussed in the same way as the Makerstoun 
observations, and the temperature coefficient obtained; the observations being 
corrected, the same law was deduced as from the Makerstoun observations.* Not 
only was the resulting law the same, but the monthly changes (omitting the 
secular variation) were nearly identical. 
12. In 1846 I was able to confirm this law by the discussion of the Maker- 
stoun observations for each of the years 1843, 1844, and 1845.+ Iwas able in the 
following years to show the same law from the Makerstoun observations, and 
even to obtain it from Dr Lamont’s observations made at Munich by a wholly 
different apparatus.{ I shall examine this question now more fully, and first 
consider the observations at Makerstoun and Hobarton. The monthly means 
will be found in Table VIII., and they are projected in Plate XXIII. 
* 1845, Trans. Brit. Assoc. 
+ 1846, Jan. 5, Trans. Royal Soc. Edin., vol. xiv. p. 99. The Toronto and Makerstoun results 
are projected in Plate III., vol. xiv. 
t Makerstoun Observations, 1844, p, 357 (foot note). 
