diurnal variation of the magnetic needle , &c. 339 
8' as the difference between the maximum and afternoon 
minimum : the corresponding differences in the table are, 
21 0 10' and 18 0 20', which have the same character, but are 
not in the same ratio ; so that the ratio of the intensities of 
the poles in these experiments, is not precisely that which 
the observed diurnal changes require. 
Observations near London, variation 24 0 36' JV. I have al- 
ready mentioned the reason that I have not been able to refer 
more particularly to the extensive observations of Colonel 
Beaufoy ; however, the maximum east and the maximum 
west in those to which I have referred, appear to have hap- 
pened earlier than those, at the same time of the year, when 
the variation was 19 0 W ; and in this respect they agree with 
the results in these experiments. The time of the evening 
minimum west, n h P. M., also coincides with the time at 
which Colonel Beaufoy states it to have occurred. The ob- 
servations which I made in 1823,* on the deviation of the 
^needle when under the influence of magnets, are of too 
limited a nature to draw any very decided conclusions from 
them ; but the course of the daily variation, as exhibited in 
the diagrams, agrees remarkably with the results in the 
table. 
There is one circumstance in which all the observations on 
the daily variation in this latitude most strikingly correspond 
with the results in the table : little change takes place in the 
direction of the needle during the latter part of the evening 
until about five o’clock in the morning ; and, from the results 
in the table, it appears that this would arise from there being 
a small maximum easterly deviation about n h P. M., and an 
* Philosophical Transactions, 1823. 
