ON BRITISH COLONIAL MAGNETIC OBSERVATORIES. 3G7 
they will probably conduce (with others discoverable by investigations still 
in progress) toamore intimate knowledge of the magnetic state of the moon, 
and may then receive their explanation. 
The two extreme easterly elongations take place at each of the three 
stations of Toronto, Hobarton, and St. Helena* (the Cape of Good Hope still 
remains to be investigated), at nearly opposite points of the hour-circle, as 
do also the two extreme westerly elongations; but at each station the elon¬ 
gations in the two directions are not of the same amount. At Hobarton and 
St Helena, both in the southern hemisphere, the westerly elongations have the 
largest values, and at Toronto, in the northern hemisphere, the easterly (speak¬ 
ing always of the north or marked end of the magnet). The lesser elongations 
are in each case about two-thirds of the greater. There is also another well- 
marked feature of difference at the different stations* in regard to the lunar 
hour at which the extreme east and west elongations occur. At Toronto the 
easterly elongation* take place ulmost exactly at the timps of the moon's upper 
and lower culmination, and tho westerly elongations at the intermediate lunar 
hours of6 h and I8 h . At Hobarton the westerly elongations occur about two 
hours after the upper and lower culmination*, and the easterly elongations 
about two hours after the lunar hours of 6 h and 18 b ; whilst, at St. Helena the 
westerly elongations occur about two hours before the culminations, and the 
easterly extremes about two hours before 6 h and 18 h . It is, perhaps, from 
such differences as these, in the effects produced by the moon's influence at dif¬ 
ferent points of the globe, that we may most hopefully expect to obtain a more 
intimate acquaintance with the moons magnetism, to which they appear to be 
ascribable. But before this investigation is entered upon, we have yet to learn 
thn corresponding effects produced iu the two other terrestrial magnetic 
elements, viz. the inclination and the intensity of the force, by processes 
™ necessarily occupy much timp, but are in progress. 
I must not, however, omit to notice a very Important fact, viz. that in the 
terrestrial magnetic variation occasioned by the moon, there is not the 
*yhtcKf trace of the decennial period which is so distinctly marked in all the 
venations which are connected with the sun. 
In the endeavour which I have thus made to meet the wishes of those who 
considered that some account, however necessarily imperfect, ought to be now 
given of the progress which has been made in magnetic science, by the aid 
o the establishments which were so greatly indebted for their institution to 
e British Association, I have confined myself strictly to one branch of the 
iquiry, which I selected as being the most likely to interest the greater 
mn or o! my auditors. Strictly as I have done this, and carefully as I have 
imH 0 V °| Ure ^ t0 88 a* the subject would permit, I still Feel I have 
onlv i* 1 • Cf ^ eman( * 00 J‘ our attention than L could have wished. I will 
othprWn therofore, in conclusion to remark, that the extension, to 
in our ^ ^ tllC solar R y« tem » ol forces which we perceive to be in action 
Porta t° Wn ? anet ’. caum,t be regarded otherwise than as one oF the most im- 
rMearch^ 11 ^ cou * 1 * he hoped for from the prosecution of a scientific 
bodiL^f t u ater i al su ^ stanccs i solid, gaseous or liquid, of which the other 
those whi .1 ° 80 c J s >'. stem ure composed, whether identical or otherwise with 
nor do wa! " C UK ’i U °,M r ° W11 P* anet » we have extremely little knowledge; 
tiou whiMi ^ eai t0 >e . 'k e ? to '“crease it by auy means of direct observa- 
We cai1 anticipate; but it is otherwise in respect to the forces 
* Phil. Trans. 1853. 
